really what you should try is looking up bicycle shops or local bicycle mechanics. or PC repairshops. they are giving away the "dead" cells for free.
what most folks do, and what you can do aswell. it's labor intensive, but very rewarding aswell.
just make sure to recycle all the scrap correctly! really dead cells in the battery, old unwanted cheap BMS in Electronics, scrap nickle in metal and plastic in plastic bins. be good to the inviroment ^^,