Roadtrek Battery Isolator Issue

I have a 1998 Roadtrek 170, and the battery isolator which connects to the alternator, and then outputs to the vehicle battery and house battery is failing.

The part from Roadtrek is $414.00 which seems quite high.

Have any of you found a more reasonably priced unit on the internet?

Thanking you in advance for your valued assistance...................Rob