Round belting, the staples and the tool for installing them (all
types) are sold by McMaster-Carr.  Here is the start page of the
belting sections http://www.mcmaster.com/#round-belts/=pmvpyu 

They have all types and materials.  The tool for joining the leather
belt is towards the bottom of the page.  I bought mine 15 years ago
and the price hasn't gone up much.

You may also try a local butcher/baking supply as I was told that
a lot of the machines used still use leather belts and they can
sometimes make up any size belt.

Glen R. Perye Jr.