Batteries for older consoles (as far back as the GBA, I believe) are still manufactured by Nintendo, but getting hold of them is a bit of a crapshoot. Stock varies a great deal from region to region and you usually need to keep checking back on your country's Nintendo online store to see if there are any available. It's also going to be even more difficult than usual during the pandemic - in fact, I don't believe Nintendo are shipping anything anywhere in North America at the moment, regardless of stock.
In my opinion your best bet is to look at replacement batteries from third party manufacturers. In the past I've had good experiences with the ones made by Ostent; I've bought batteries from them for both my original 3DS and my New 3DS and so far I haven't had any problems. They also come prepackaged with the right screwdriver to open the battery case, which the official Nintendo ones don't. They have a listing on Amazon that might be what you're looking for, but unfortunately it looks like there are some states they won't ship to - again, possibly because of the pandemic.
ETA: Also, just to clarify, don't buy anything that doesn't specifically say it's designed for the DS (or DS Lite if that's what you've got). All of Nintendo's consoles have their own uniquely-shaped battery packs - you can't just get a generic one and expect to be able to plug it in. That would be too easy.
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I know it's a bit late, but you could theoretically pick up a used DS and take it's battery out to use on yours, that way you get the battery and still use your system. You could even potentially sell back the DS somewhere lol My PSP battery inflated and would not fit the system, I took it out and sold it to Gamestop and they didnt check
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^ I'd avoid doing that. Lithium batteries don't last forever, so buying a used original DS unit will almost certainly get you a battery that's over a decade old, with a potentially high number of charge cycles already counted.
Getting a replacement battery straight from Nintendo would be the best way to make sure you're getting one that will last for years to come.
Well, I actually picked up a new battery from Ostent. I would have preferred from Nintendo, but beggars can't be choosers. So far, it's working. I mean, I haven't played for long, but the battery light is staying green.
"I know it's a bit late, but you could theoretically pick up a used DS and take it's battery out to use on yours, that way you get the battery and still use your system."
Nice idea, except my DS was already used. My original DS got broke. I accidentally dropped it, and it was already pretty old.
"Getting a replacement battery straight from Nintendo would be the best way to make sure you're getting one that will last for years to come. "
I did check their store, but I didn't see ones for original DS. Then again, I probably wasn't looking in the right place. Theoretically speaking though, as I do have my 3DS and Wii U to consider also, would I be able to actually call them and check to see what they've got if the store doesn't show it? I know they're probably not shipping anywhere right now (thanks COVID-19).
I know it's a dumb question, but I'm kind of in uncharted territory for me. Usually, I'd pick up a pack of AA's when I needed batteries.
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