Grendel and PPC brass would work since it uses the same base as 7.62x39. Other similar-sized brass should be able to resize to fit. I've collected over 1k of x39 brass so I'm all set
I'm not going to ream my own dies - I don't believe my mini-lathe is up to the task and I really don't want to risk damaging the reamer or the dies. My luck I'd end up reaming the die out of round and wonder why all my case necks aren't concentric.
I'll make some calls later this week to get some quotes.