The best I have found is essentially surplus stuff. Non-corrosive doesn't seem to be to plentiful and it might be around $1 a round. Try Tulammo or Barnaul, that's all I know of.
Someone correct me if I am wrong.
I read it the topic as 7.62x64r. Sorry folks, I just started working nights and I'm kind of wonky.
7.62x54R ?Don't worry, everyone becomes a bit spacey with sleep deprivation. For the record, 7.62x64 (rimless) would be the 30-03 with the revised 30-06 being 7.62x63.