The battery in my Walkman (Sony NWZ-E345) is getting weak. Replacement batteries are not available from Sony, and it's not really worth it to send a $100 player for out-of-warranty service. How would I find a Li-Ion battery of the right size? It's almost square (38 x 40mm) and very thin (2.5mm), has 2 wire leads. A search on eBay ("li-ion battery" in the "batteries and chargers" category) returns 2500 results, but I didn't see anything that would fit. Is there a secret place where one could find or cross-reference a battery of a certain size?