Reloder 15 seems to becoming pretty available lately, along with Norma 203-B, which if it isn't the same powder as 15 is pretty darn close.
Either works great with 286's in the 9.3x62, as well as 250's. Nosler lists 58.5 grains of RL-15 as the highest-velocity load with 286's, and Norma lists 58.0 grains of 203-B as max. Both load are around 2400 fps, and another grain or two gets velocities in the same range as Big Game. RL-15 is also the most temperature-resistant of the older Reloder powders, if that's a factor.
A lot of popular powders are hard to get right now, but some are starting to appear. The repairs to the factory in Belgium where Ramshot rifle powders are made are apparently done, as new TAC is showing up. The people at Western Powders tell me the factory will start making the other Ramshot powders as soon as some of the demand for TAC is filled. I'd guess that Big Game would be the next in line, but don't know.
It seems like Alliant got unlucky about the timing in introducing some of their new powders, and had to scale back to meet high demand for some of their older ones--like a lot of component companies are doing.
