Air horn compressor belt?

[shantyboat]

I've got a houseboat with a Hadley mini compressor with belt. Apparently the "old style" from some unknown time deep in the past. For trucks, RVs and whatnot. Hadley doesn't stock this and in fact has no information.

Belt's broken and I have no idea how to find a replacement aside from a trip to the auto store today.

Any ideas?