Timing belts are readily available from most power transmission dealers
And from McMaster-Carr. You need to know the width, pitch (distance
between the teeth) and number of teeth.

A common smaller size is the XL type. The teeth are 0.200" apart. They
are available in different widths and number of teeth. A chart is shown
at
http://www.powerdrive-belt.com/new/product/6Bk9BqYnnux4BH9pQuw7Fd3U9M0bHH.jpg
 

The catalog page for XL belts from McMaster-Carr is shown at
https://www.mcmaster.com/products/timing-belts/xl-series-timing-belts-8/ 

Bill Klinger
Flippin, Arkansas
http://klingerorgan.com/