I set up a tank around the beginning of this year (January/February?), and I'm fairly certain I bought MGOCPM at an OSH.
I was at the emeryville Home Depot recently (either last weekend or the weekend previous), and I'm fairly certain I seen a big bag of MGOCPM. I didn't look closely, so I could be mistaken.
Maybe there's also a chance that if the chain doesn't carry it, some individual stores still have a pallet lying around and are selling some bags.