Hi MaskofMany,
You could look at using a TieClip/Lavelier microphone like those TV presenters wear mounted in the helmet and connect it to a Voice changer then plug it into a Marshall MS-2 Micro Amp amplifier.
The MS-2 was designed for guitarists to carry round with them and the amplifier clips onto your belt. It should be a bit louder than the Voice changer kits and modules available. (Plus it is battery or mains operated and has connections to plug it into a bigger amp).
I have an MS-2. That would be plenty loud. Do you play guitar For?