As with a lot of 99c Only Store [99only.com]
items, YMMV. This is not for generic 99 cent stores but stores branded "99c Only" with that linked logo. There is a store locator in the link.
(according to wikipedia, these stores are only found in "Southern California, with others in Nevada, Texas and Arizona").
Inventory seems to be moving quickly at stores, so if you're having trouble keeping up in this thread, I'd suggest just visiting any 99c Only Store within a couple blocks of your usual route, every 2-3 days, and then using this list [portalcharacters.com]
to see what other sets may be available, and use the thread search to see if anyone's mentioned it in your local stores. (You could use the official LEGO website, but it's hard to see the whole list all on one page).