Darrell, I've tried several different systems for my TK, some work better than others obviously, but it's been trial and error. I DO like this gizmo I found through the Mando Mercs site. It has a volume control, which my wally world voice changer did not.
I'm not sure if this is allowed on the boards, so remove if applicable.
look at fleabay under star wars costume mask voice amp. It's $10, worth much more.
You just cut off the piece that attaches to the firefighters air mask. It has a decent mic, or, just cut the wire and rewire your preffered mic. You would'nt want it in your helmet, too much feedback, probably not enough room. It would work carried on your person somewhere. I use mine with a headset mic.
I also may gut a guitar EQ effects pedal and use it to EQ my voice to the correct sound. ( I used to be a sound guy at a music club, I like tinkering with this stuff !)
Good luck, have fun experimenting !