I don't know of anyone who stocks sch80 locally, but you can order from places like usplastics.com or mcmaster.com. (you need to create a buisness account to use mcmaster, but that's easy. I suggest "Charlie's aquatic supplies"
)
That said, there is no reason to use sch80 for aquarium applications because nothing we do uses the pressures that sch80 is designed for. On the other hand, there is a good reason NOT to use sch80, and that is the ID of any given pipe size is actually smaller than the same sized pipe in sch40 (due to the thicker wall thickness). Also sch80 costs more. You can get sch40 pipe in grey if that's why you are looking for sch80, but you will have to order it online.
Tropic Isle carries loc line and lots of other fittings and whatnot, but of course everything is WAY over priced. All the loc line and other fittings are behind the fresh water tanks on the right side of the store as you walk in, you'll see everything if you look for it, but it's not openly displayed on the store shelves.
HTH