Old battery packs and laptop batteries (Reepham NR10)

I'm looking for used 18650 Li-ion batteries to use at The Fixery, a repair café in Reepham, to give a new lease of life to old cordless tools and vacuum cleaners. New cells are typically too expensive for this purpose, but old battery packs often have enough life left to be worth re-using. They need to be cylindrical cells like these, not the pouch-style batteries that slim laptops often use.