cliffinnc-
I hope someone, perhaps one of our dealers, can help you find the specific OEM part.
If not, is it a very unusual type of belt?
Perhaps a major belt manufacturer, like Gates, could measure the dimensions and find a suitable substitute.
I rather imagine belts are like bearings. There are thousands of types, and it is likely that a similar product can be found and used.
You might try asking Raymarine who made the belts for them and then contact the manufacturer and see if the belt or a suitable substitute is available from them.
Good Luck!
Joe. :teeth :thup