Homebrew PCBs

I have some 5 mil thick SS clad (0.5oz) I got off ebay.  Once etched
it's pretty flexible (0.5" diam bends) and somewhat translucent, it
might be acceptable for your purposes, but it's not as flexible as
"flex" is.

Advanced circuits does flex protos, but not inexpensively:
http://www.4pcb.com/index.php?load=content&page_id=133