I found this mic/amp setup on ebay and bought one. It is very loud and compact 1"x2 1/2"x3 5/8" with a 30" cord.If you look at the pic the housing around the mic tip goes inside the gasmask but the mic will come out of the piece. It cost $9.95 and the shipping was free! just wanted to share the find for those who need one. It doesnt distort like the toy ones do either. takes a 9 volt battery. I'm not providing a link to the site but I will tell you what to search for "star wars stormtrooper vader mask helmet voice amp new!"
I dont think I'm breaking any rules since I own the one I took the pic of?