I ran across this tonight. I think it's anyone's best bet for a THC.
The pros:
It's USB so it's simple to implement
It has a simple connector to add up to 10 buttons
It's cheap - $15 + shipping.
The cons:
It gives one 2 axes so you'd have to implement Z with the additional buttons
It's in a plastic casing to look like and arcade controller not a THC
The handle doesn't translate but rotates like an arcade controller
Check it out: http://www.legacyengineer.com/store.html
The pros:
It's USB so it's simple to implement
It has a simple connector to add up to 10 buttons
It's cheap - $15 + shipping.
The cons:
It gives one 2 axes so you'd have to implement Z with the additional buttons
It's in a plastic casing to look like and arcade controller not a THC
The handle doesn't translate but rotates like an arcade controller
Check it out: http://www.legacyengineer.com/store.html