Like he said what you need is any Drum Brain. Triggers are really just any transducer and even microphones will work. One guy I read about rigged up his mixers inserts to send the signal to a drum brain. He simple patched into the mike channels from a fully miked up acoustic kit. The drummer will be totally unaware.
You will have to go into the editing of the brain and adjust the sensitivity.
I had 100% success using this old tape deck mike from the 60's. It came with a 1/4" jack so was plug and play.
But I changed that out for this $16 acoustic guitar PU I just stuck on the snare head.
http://www.guitarfetish.com/GFS-Surface-Mount-acoustic-transducer-25mm-Preamp-plug_p_6423.html
I removed the electronic snare from my Yamaha DX 500 kit and I use a real snare. I mike the snare as well as track it with midi via the transducer PU and the brain. I'm trying to figure out how I could do this with a hi hat.. Skins are easy but cymbals are tricky.