Does anyone know of a company other than the dealer that sells kits or parts for this transfer case? They want like $300 bucks just for the chain!

Try E_ Bay they sell complete kits or just the chain.

Here in Phoenix, there is a place called RPM Automatic Transmission Parts. They have TC parts there as well and have wholesale pricing. They are not national though so I don't expect them to be in your area, but you may call a trasmission shop and if you hit someone nice enough, they may tell you who a good local distributor is.