I try to keep a fairly decent stock of various spare batteries that get used here at least on occasion "in stock". Typically I try to keep several coin cells, ( CR2032, CR2024, LR44 as examples) and also a few more esoteric batteries such as the A123, and the one I'm buying today, A21/23.
Retail is expensive, and not that convenient for me. Also, because the nearest town is not a big city, some of the rarer types are either harder to find, or don't turn over fast enough so I'm often buying a older battery for stock purposes, so I've moved to trying to get them via mail. I've tried buying these on Amazon, but it's really hit or miss as far as the quality of what shows up - in a lot of ways it's like buying memory cards - there are a lot of sellers out there pushing products which are not fit to be sold. Counterfeit. Old Stock, Used (yes, used batteries).
So the question is: Has anyone found an inexpensive but consistently good mail-order vendor of batteries?