Have you tried a sherwin williams store? That's where I got mine locally...
SW Aero products is the ticket, automotive folks I spoke with locally couldn't help. They found a distributor 90 mi down the road that has more than 50 gal in stock. Tricky not being a commercial operation, but when I told them I was building a Vans RV their attitude changed. It will be delivered to my shop tomorrow.
FWIW: P60G2 is ~$119 a gallon, R7K44 ~$60 gal, need 1.5x primer so you need to buy 2 gal. FedEx gnd shipping only.