Thanks for the tip on the thin section bearing - only $16! Last time I bought one of those (maybe 20 years ago) it was several hundred dollars. (The miracles of Chinese manufacturing.) I may need a slightly smaller OD, but I can probably find a 60mm ID bearing that would still leave me enough room for mounting hardware for the inner race.
As for the belt path, I just laid that out using multiple planes that all lie on the centerline of the belt. To sort out the length, I didn't use any sort of path length constraint (I'm not much of a Solidworks wiz) - just a little trial and error.