I have several pieces of older Troy-bilt equipment and i've had good luck purchasing belts from Napa Auto Parts stores. The two stores in my area can cross referance the Troy-bilt number to a Napa number. In fact i just replaced the two belts on a Troy-bilt walk behind mower last week.

I found belts for Troy-Bilt Chipper/shredder from JayDee
Enterprises Inc at www.jdv-belts.com I purchased belt
PIX-AA55 it's a double sided vee belt and it works fine. Off hand I don't know the price but their email addy is jdvbelts@earthlink.net Hope this helps you out.

I have a Trot Bilt Super Tomahawk chipper/shredder.
The question is what should the chipper knife clearance be. If someone could measure it and reply, I would be very grateful. The holes in the main shaft set the flail/chipper location and the old shaft was very bad.
This machine came to me with a bent main shaft and bad main shaft bearing. I had to cut the ends off the main shaft to get the flail assembly out of the machine. I have made a new shaft and it all looks good and should work well.
I am running 1 in shaft bearings on the new shaft and that should improve the life.
If anyone needs a shaft or other machine work done to extend the life of their machine pleas send an E Mail. I also have manuals and numerous sources for parts.
I make flails out of old truck springs and harden them.