FWIW, I spoke to one vet who told me they used to have those grips fashioned out of the broken windows from downed aircraft...
Here is a sample image of a grip that was on a Luger Internet auctioned last year...
Very crude looking, but I guess if they were properly polished, they wouldn't look too bad on a cutaway model.
-JS
http://boards.rennlist.com/upload/Transparentgrips.jpg