eBay USA has them. I searched "Apple M0100":http://www.ebay.com/sch/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=apple+m0100&_sacat=See-All-Categories.

There's probably more listed under different names. That search turned up listings costing less than a new mouse from The Apple Store at least... It's small so international shipping probably wouldn't be horrible.

You could also try wanted ad in The Trading Post here. I wish I had one to spare.

Good luck!