Marcus,
Don't be so sure a suitable belt exists for your engine. I replaced three of the four belts on my 1G-GZE and while the S/C and the air con belts could be matched exactly, the only alternator belt that existed here in Perth was 10mm longer than the original one. Its not a problem with an alternator as you can adjust its position, but I was glad they had an exact match for the S/C belt, which by the way is a 5PK940.
Cheers,
Mitch.