OK admit I don't carry the tools either and the Harleys in question have modified engines and the belts just don't hold up.
It does depend where you ride/live. Most of mine is in rural areas. Calling a garage and expeting quick service is probably asking too much. The chance of a chain letting loose is pretty slim (vs a belt) and most local farm equipment shops or farms could change a chain in few minutes without too much hassle.
If you had a QPD you would probably have to carry a spare belt anyway as its probably not a standard issue.
