Replacement for Dell XPS 15 9550 battery

I have an XPS 15 9550. The battery needs to be replaced because it seems to be swelling up.

The part I need to replace/fix this issue (which is either a design flaw or  manufacturing flaw and which is obviously a known issue even though Dell denies it) is part no. 1P6KD, a Dell 84 WHr 6-Cell Lithium-ion battery. Dell does not offer this part anymore, apparently. I can't find a replacement of similar oomph, only lesser versions. Anyone have a replacement that would work? Thanks.