If you have machining resources and want to use 20 degree pressure angle 32 DP gears, you can order from McMaster (
http://www.mcmaster.com/#standard-gears/=tbp9wu)
SPD-SI has what you need (gears->spur gears->metal) in more sizes, but they aren't the fastest supplier.
You may also be able to find it on amazon.com, but I'd recommend purchasing only from Boston Gear or Martin, and avoiding Chinese gears or gears from "Ametric", which has horrible variations between gears.
For both you'd likely need the proper size reamer, also available from McMaster.
254 belt pictures from Pat Fairbank's photos:
https://lh5.googleusercontent.com/--...o/DSC_4505.JPG
https://lh3.googleusercontent.com/-s...o/DSC_4515.JPG
https://lh4.googleusercontent.com/-6...o/DSC_5067.JPG