Primers, like ammo, have been in short supply for many months now. Powder availability is still fairly good. Several of the major primer brands do their manufacturing out of the U.S. (surprise). Predicting the restocking schedule always seems to be an iffy proposition.
Keep an eye on the follow sites and buy in quantity when they restock:
powdervalleyinc.com
grafs.com
midwayusa.com
midsouthshooterssupply.com
cabelas.com
Primers are actually a good investment commodity. As long as you can store them in a cool, dry place, they'll keep for decades and never lose value.