We don’t know about what you’ve been seeing, but buckshot loads seem to be among the most difficult ammunition to find lately. The good news is that GunMag Warehouse has it in stock, at least for now. They’re selling Federal Power-Shok 9-pellet 00 loads in 5-round packs for $9.99 a box.
Check their ammo page for other calibers as well as they have things like 12ga slugs, 55gr .223, 230gr .45 ACP and others in stock, too.
You probably don’t need to hear that they won’t have them in stock for long, but…they won’t have them in stock for long.