Do you live in the US?

If so, I don’t think you’ll really need a protected cell, since the light always has a micro-USB charging circuit, and protected cells won’t really be needed.

If you want absolute highest capacity, I would get the Samsung 35E:

If you want something for quite a bit cheaper, but with good capacity, I would recommend the Samsung 29E:

Shouldn’t be a problem with 3A and less lights, like the RJ-02.

If you want something even cheaper but with slightly lower capacity, I would be getting the LG M26:
https://liionwholesale.com/collections/batteries/products/lg-m26-2600mah-10a-flat-top-battery-genuine-and-tested?variant=12401785012318