Along with Brecoflex, B&B Manufacturing and Rainbow Precision are sources I use for belts & pulleys.
For pulley mounting where a taper-lock or similar tapered bush isn't available, keyless shaft bushings are an excellent choice. Very strong shaft grip, excellent runout, and easy to use if you're making your own pullies from pre-hobbed blanks (or raw stock)
Before you commit to a timing belt, consider a poly-v (milti-rib, many names) profile. They are considerably quieter than timing belts, and can still be used for a rigid-tapping setup if you put an encoder directly on the spindle. Downside is they require a bit more belt tension - and thus bearing loads - than timing belts.
If you absolutely must have a timing belt and are willing to spend a bit more than typical HTD prices, Continental's SilentSynch are almost as quiet as poly-v's. Downside is the pulley selection is less broad than with standard timing belt profiles and they can get pricey.
