You can find an adapter, but the one I ordered from Amazon was 20 gauge crap.
I haven't been able to find one. Even if I did, I wouldn't use any 20 gauge crap. I'm thinking about maybe building my own using 16 gauge wire.
I have been able to find 8-pin Y splitters that look rugged enough. Then from there go to 6 pin with a 8 to 6 adapter. However, that would cost about $20 in cables for each 8 pin I wanted to split up, and I have 8 of them. That's $160 total, not really sure I want to go that route, not only due to price but also because more connections equals more possible points of failure.
I may just go with some 6 pin Y splitters since I'm running a Seasonic PSU, and I know their wiring is up to par.