Yeh, you can order 3, 4, 5, 6 or 7 panel kits and additional panels can be purchased separately. But it's more expensive to add panels, so the 5-panel version for $427 seems the best deal - assuming you actually use them all.
 
Our biggest concern is that in isolating the drummer from the audience we don't want to also isolate him from the band. I don't see that as a major problem, because even with 5 panels it only wraps around to the hi-hats, not all the way to his ears. He should be able to hear our amps just fine (I use two QSCs on poles set behind and on either side of him). We'll probably just need to give him a vocal monitor (he doesn't use one now, as he doesn't sing).
 
I checked Craigslist but found no drum shields. If they were really awful, I'd expect to see some there. Kind of like Nordic-Track machines - you know, things that seemed like a good idea at the time but invariably end up in a garage sale. I'm assuming the lack of second-hand shields means people who buy them actually use them.
 
I've had several people question how much attenuation they really impose (echoing MBGantt's comment above). I found a YT video where they showed before and after measurements with an SPL meter. The basic 5-panel setup gave about 8-10 dB reduction. (That's definitely significant. Open one of your projects and lower the drum bus by 8 dB.) However, it's not going to be a linear reduction; low frequencies are going to penetrate a piece of plexiglass like it wasn't even there. That's OK, though. I'll be happy if it merely lowers cymbal bleed into the vocal mics.
 

Jim Roseberry
FWIW, I play out quite a bit here in Columbus, OH.
We're fortunate to have a fantastic drummer... who doesn't play particularly loud.
Sound guys love him (super easy to work with)… and his drums sound great mic'd.
 
We've seen numerous local bands where the drum volume  (or volume period) is upsetting the audience/patrons.
Literally chasing them out of the room...
If that's happening, (IMO) you've got to address the issue at the source.
Blastix instead of regular sticks can help, but the player needs to be mindful of what's going on around him.
Drum-shields can help... but I still think the ultimate answer is the player learning to adapt.
The days of 8x12 full guitar stacks and 8x10 "Fridge" bass cabs are long gone.
You can still be a "rock band" and not blow everyone away.
 
A band is essentially a team.
Cliche'... but everyone needs to be a team player.
If one instrument (or vocal) is grossly loud, it diminishes the whole.
It may take a while, but I'm sure the drummer could learn to fit within the "volume context" established by the rest of the band (instead of vice-versa).
 
Things that chase folks out of a club:

• Feedback
• Grossly loud drums/guitar/PA
• Rush tunes

 
 
 
 
 
 
 

 A school band director's dream. There is a difference from playing beats to playing music.

LOL, "Rush tunes" made me chuckle, but I'll admit I am one of those who have walked out due to "grossly loud."

So we did our experiment yesterday with an improvised drum shield. The results were inconclusive.
 
I used an A-weighted SPL meter to compare levels under a variety of combinations: drums only vs. full band, quiet songs vs. loud rockers, sticks vs. hot rods, each repeated with and without the shield.
 
We all agreed that the drums sounded better and the drummer played better with sticks rather than hot rods. The hoped-for result would have been that the shield brought the volume down enough that he could play with sticks all the time. Sadly, that was not the case.
 
Here are a couple examples of my measurements. These songs were chosen because they're dynamic, with quiet parts and big crescendos. 
 
J.Joplin's Piece of My Heart: 96 dB - 109 dB w/o shield, 94 dB - 108 dB with shield
Summertime: 90 dB - 105 dB w/o shield, 91 dB - 104 dB with shield
 
So the overall volume change was trivial, falling within the margin of normal playing variability.
 
However, what I couldn't measure with the SPL meter was the sense of mix balance. With the shield up and using hot rods, the drums sat much better in the mix. 
 
Bottom line is that while drum shields do help, they are far from a panacea. Hot rods over sticks provided a much greater volume reduction than the shields.
 
Our jury-rigged shield was made from old windows and duct tape and was only 8' in length. A proper 5-panel store-bought shield would be 10' in length and possibly made of a slightly denser material, and therefore possibly more effective. Enough to justify $400? Don't know.

I'd just buy the guy an electronic kit if I could afford it. But while price-performance ratios have steadily improved over the years, it'll still set a person back 2 or 3 grand even before looking at amplification. 
 
I did a gig once with a single Bose stick tower handling keyboards, guitar, drum machine and vocals. Obviously, it was a low-volume gig, but the amount of output from that little thing was impressive. No distortion, no feedback (even set up behind us), and it filled the small room nicely. My only complaint was it didn't have enough high end for piano, but the bandwidth was more than adequate for guitar and vocals.

Vibes
I have played drums all my life and have no problem playing at any volume. 

Need a gig?