Follow twitter accounts that post announcements of upcoming restocks (search for "ps5 restock"), and turn on notifications, and then try at the posted times. Rinse/repeat. Took me a couple of weeks (ymmv, obviously). Yes, it's frustrating that, with the chip shortages and pandemic and whatnot, production still hasn't caught up with demand.
They apparently had PS5's available at walmart at noon(Pacific time) also had them 10 minutes after that..its how I got mine back in Feb..once you have it saved in your "List" the next time it appears just quickly add to cart and check out