Dude, I just made one for a tribute show this weekend past.
A 10 dollar driver, some tubing and some plumbing, and a capacitor to kill everything under what the driver can handle...
Here's the driver I used
http://www.partsexpress.com/pe/showd...number=260-097
You might wanna try one with a little better low-end response...but hey...this one was a tad harsh. The real trick is how it'll sound going thru a small narrow tube to yer mouth.... call it trial and error.
all in all, 20 bucks (and a guitar amp to drive it)
cheesy easy. Talkboxxes...not real great for bass, but with guitar it's fun...if you wanna jam the AeroFrampton tip.