SiteOne has different pricing tiers for their customers and you'll likely get the highest. But no harm asking if they can mark down for you, which managers are given the discretion to do. They also have the straight Teammates tall fescue and might have other tall fescue mixes or varieties as well. Bags are all 50 pounds as far as I know.
Edit- we have some Zoysia in my area. Good luck crowding it out. Probably not worth the effort.