Yes they do, but there is a very limited selection. 50th package and various punches. Inside next to the photo shop on Main Street in Disneyland. Also here and there in Emporium and the shop on the end near Lincoln Theatre. I don't know about California Adventure. You can also call DeliverEars and see if they have anything you didn't see in the parks.
The World of Disney in DTD and Greetings in DCA have supplies. All the papers come in kits (they're $15--they also include a couple of sticker sheets) and scrapbooks are $25.
I really looked last time I was there, and it seemed really really limited. (I was not looking for the paper packs, and it seemed like all the stickers I could find or wanted came in one.....In fact, I ended up not getting anything but some postcards. Oh well!
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