The SeaCon 8-pin pigtail fits in the BR large penetrator. It is a very tight fit for the wires though, and seems like not enough room for a proper potting in the tube. If I had to do it over I would probably strip the insulation from the wires and cover them with thin-wall heat shrink, to open up more room for the epoxy. In the end I gritted my teeth and spent the money for a SeaCon bulkhead fitting.
If you are only going to 30’ depth and willing to drill a custom endcap you could probably run the pigtail through an IP68 or IP69K rated cord grip. McMaster-Carr.