Butcher & Packer has the best prices on hog casings.
I get collagen snack stick casings from the Sausagemaker retail store that's about 4 miles from my house.
I do buy Syracuse Casings in a tub here at the grocery store if I run out of others, only problem is...they're not sized.
Tub is supposed to have enough casings for 20-25 lbs. of sausage, but I've found enough for 30-40 lbs. or more sometimes.