I've also noticed that there are small dealers on eBay selling batteries at very attractive prices. I'm concerned about the quality, though; I've heard of "generic" Chinese-made batteries that leak or are otherwise safety hazards. (This was in reference to more common general-purpose batteries, like AAs or D cells, but the same could be true for button cells.) Therefore, I prefer to buy batteries from well-known manufacturers, at least when they're going into anything I care about. I don't cherish the thought of cleaning nasty goo out of a camera's insides.
Even for those not in Europe, the Small Battery Company has an excellent cross-reference tool. I've used it often to find what I need, even though ordering from them would make no sense for me, since I'm in the US.
I've been having trouble finding the old standard button-style MS76 or the lithium 3v equivalent, which replaces two MS76's. My Minolta flash meter takes 6 MS76's, Nikon FE2 and Leica M6 both take 2. They are getting scarce.
I currently use Energizer 357/303 Silver Oxide batteries in my cameras and in my HP hand-held calculators. These 1.5V button cells are a direct replacement for the MS76.