Where to get T-Case seals

[Destructo]

I have a seal or gasket go out somewhere between my t-case and transmission, leaks pretty bad while the engine is running, I gotta fix it quickly because I need the truck for drive next weekend for a 4x4 event which it will be towing the samurai down.

I don't know if Advance auto carries these things or not, or will I have to get them from a specialty drivetrain shop?

My front output seal and rear slipyoke seal were leaking some, so i'm going to fix those since I will have to pull the t-case anyway.