Hi Scott,
I noticed a price you found for the 25cc in a previous post (near the top of this thread). I got my first one from www.gcbmrc.com for $210.

Of particular note:I think Bill Carpenter at C&H ignition mentioned he has a bunch of craft with this engine installed. Contact him at www.ch-ignitions.com or 307-857-6897. In that he supplies most of the gas engine manufacturers with ignition gear I would think he would be an excellent source of info for you.
Doug