Bob has probably done more of these repairs than the rest of us combined. Even before reading his reply, my suggestion was going to be knurl the shaft and apply locktite... always nice to see his confirmation of an initial reaction. Any chance the second shop will do that for a similar relative cost/discount?
Minimize your cost now to see if you can get a simple fix that works. Then keep your eye out for a bargain motor going forward that you can buy and stick on a shelf if needed in case the cheap fix wears out. No way I'd pay close to full motor (ebay) cost to put one together that's a kludged fix itself. You can either pay now for a good motor or pay later if necessary, but I don't think it makes sense to pay now for a motor that may or may not eventually need replacing.
Hope this helps. Good luck.
Know, think, choose, do -- Ender's Shadow