Is there such a thing and where can it be found?
 
Online documentation says there is but I don't have it to my knowledge.

I don't think the version that comes with Sonar/CbB can do that, however you have options.

I think they haven't updated the documentation yet. 
 
Here's one that might fill the gap until you get the other one sorted. It's free.
BASS
 

The Cakewalk SI that were bundled are only VST instruments as far as I can see.
 
If I don't feel like launching a full DAW host to play a .dll plugin instrument, I use the free VSTHost, which includes a VSTHostBridge32 in the 64-bit version, so it will run 32-bit and 64-bit plugins.  Handy for old 32bit gems like Minimogue-VA!  It is a little more advanced than SaviHost, because it allows you to chain plugins together and has a mixer, but it is based on the same concept.  And the most recent version is a bit newer.
 
http://www.hermannseib.com/english/vsthost.htm
 
If a plugin is available as a standalone, it is usually because it includes a custom mini host in the form of an .exe file.

Starise
I think they haven't updated the documentation yet. 
 
Here's one that might fill the gap until you get the other one sorted. It's free.
BASS
 

Hey, already had that!  I forgot that Ample installs a host for standalone use of its plugins.  Good tip!

Back in the X3 (maybe before days), the SI bundle could also be launched stand-alone.  vsthost as mentioned above works fine.
 
 

I have SHS7xl, 8.3, X1, X2, X3, Splat, & CbB all installed but can't find any reference to the EXE versions of SI.
 
I am trying out SaviHost but it seems a bit wanky and the latency is very touchy to adjust. (edited)

I've remembered a bit more.  I actually bought SI Instruments during a hiatus.  That version had stand-alone exes.  When I came back in at X3, the bundled version did away with the exes.
 
I'm not sure why the bakers decided to do this, but I remember it being a PITA.
 
 

Not something I need very often but was just curious about the stand alone feature. The SI set was released about 10 yrs ago as a package for $50 and, apparently, is still available from Digital River for $65 Canadian. Would be nice to have but not worth $50/$60 at this point.
 
I can get SaviHost latency down to useable levels in MME mode but it crashes if I try to use my onboard sound in ASIO mode. Oddly SaviHost doesn't see my audio interface tho VstHost does.

IIRC, I paid $20 for Studio Instruments back then.