I've had good luck with these so far: https://smile.amazon.com/gp/product/B081SB3DF5/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

They say they're 6Ah, but someone opened up the pack and found that it had 10 Sony 2.6Ah cells, so 2 sets of 5 in parallel, giving 5.2Ah.

They last longer than my 4Ah packs and I haven't run into any issues yet, knock on wood.