[toby]

You could try TAP on South Van Ness, they have two-way acrylic mirrors on their website: http://www.tapplastics.com/product/plastics/cut_to_size_plas...

[zten]

I'd suggest finding glass instead of plastic if you can deal with the weight in order to avoid having a distorted reflection. It should also be cheaper -- it looks like they're charging $33 per square foot for 3/16" plastic.