Where do I get drive belts for a aiwa xr-m10
Try eBay, i've been looking for these on the internet, they sell kits (long and short variety), containing several pairs of different measures (about $7 per kit), and are supposed to fit various brands and models (including aiwa).
...a hint: a belt measure tells you the diameter of the circle formed by that belt
...another hint: old belts are loose, which means they are a bit longer than the new ones, so when you select the new belt from the kit, it should be a bit shorter than the one you removed from the deck (old belt - bigger circle, new belt - smaller circle).
I'm aware that not all aiwa models are the same, the one i was repairing a while ago had a double tape deck, each deck containing two belts, one long and one short, they were a bit tricky to change, but i didn't need to disassemble any of the mechanisms, i just had to remove both decks from the housing for easier access to the belts which required prior removal of the top cover and rear panel. After that it was some 4 to 6 screws and 4 connectors (just about half less in your case, i believe).
I can't tell what your unit looks like on the inside, but in my opinion aiwas are relatively easy to take apart, but then again, i could be wrong...
Hope this helps you get closer to a solution.
regards
3rq8 (Triarcuate)