Hi, hmm the experts haven't had a chance to read your thread I think...but I'm sure someone will give you detail info sooner or later!
Anyway, as far as I know, all vespas come with leather strap that is not removable. its the evelynes that come with canvas straps that are removable! Cost of smallest size? like the mini one? I think its just under 2000 in Canada.
HTH!