Thanks, Fjold!
I have a restock notification set at nereloading. Staring down a few auctions right now. That's looking like the only way I'll get my hands on brass for this caliber. My other alternative is re-forming .375 H&H, but that will add a lot of time (and remove .375 brass from the market, screwing over the guys loading for it). I'll do it if I have to, but would much rather source factory .300 H&H if I can.