Maybe used cells out of a crashed Nissan Leaf? For new cells, probably the best option is to try and find a good deal on LFP cells, though in the U.S. at least

Maybe used cells out of a crashed Nissan Leaf? For new cells, probably the best option is to try and find a good deal on LFP cells, though in the U.S. at least they tend to be really overpriced. A BMS will be needed too.