BatteryHookup.com sells various types of battery cells.
Some are NEW and some are USED.
Sometimes, you have to crack open an old laptop cell holder ( or other plastic enclosure) to get at the cells.
They are located in the USA, so you don’t have to order from China.
I think the prices are pretty reasonable. I have ordered from them several times, and I always got what I paid for.
Battery Hookup: Genuine Lithium Batteries for DIY Projects