I just posted a couple of threads elsewhere before I was directed here. I was told that the mikes I sell on eBay for my respirator equipment work well in costume masks. I sell them for $9.95 with free shipping, even cheaper for a set of ten ($79.95). They retail for $80 and are designed for emergency response use, so they should do the trick. Search Item number: 300278137063 for the single or Item number: 300278153169 for the set of ten. Thanks again to those who have purchased them and passed the word!