It would be mighty helpful to know what size shaft you need. If its Dremel stuff then get them anywhere they sell Dremel stuff, which seems to be pretty much anywhere. If its cheap quarter inch bits you want then one of the mail order places will do nicely, and of course there is always E-Bay. If its grinding burrs you need then I'd say go straight to E-Bay where you can find absolutely every size, shape, length, and quality of bit/burr ever made. If you plan to buy one or two quality burrs you better be ready for some sticker shock though. Don't get me wrong, they are worth the money, but they are not cheap; Home Depot and Wal Mart do not sell anything that can even be remotely compared to a real burr.