Depends on your version of 'cheap' I guess. My local CTs and Sail all have .303b in stock, but at more than $1 to pull the trigger, I don't call that cheap.
Roll your own. Components in general are getting rarer, but luckily stuff that works in my enfields is available. I get great results from .313 gas checked hard cast rounds from the Bullet Barn, for example, and I'm experimenting with a few other cast round from some local folk, but too soon to make any quality statements. Brass is available, as are LR primers, and I have a few loads with several powders, some of which can still be found.