And here’s one other possibility:
If matters can’t be resolved with SanDisk, your buddy could purchase and use an external battery pack that would attach to his player. While not as good as simply replacing the player’s battery (I mean, your buddy probably would like to prefer having to attach the player to a separate battery pack), it’s a possibility.
I purchased a good, relatively small, inexpensive AA battery pack (which can use rechargeable batteries) for just a few bucks shipped. (Note: there are many of these available at eBay; try a search on"AA battery emergency charger" to find the lowest price–well under US$5, often at around $3 shipped.)
(But, I’d still telephone SanDisk about a possible replacement first …)
