This article is completely unrelated to Lippmann photography, but it's about anamorphic lenses, and he talks about prisms and where to get cheap ones. Scroll down a ways to find it.

http://www.zuggsoft.com/theater/prism.htm

But it's pretty brilliant... TROPHY SHOPS. There are all sorts of lame prism/wedge awards and you can just easily buy a blank one. These should/could work great for Lippmann viewing.