Sorry I'm interrupting your travel trailer thread, but I just did a Google search on "battery cable with fuse," (without quotes) and got a lot of hits.
Some suggestions, try an RV dealer, or a marine store.
Good luck, and all makes of RV's have batteries and cables, not just travel trailers. Hee hee!
Wayne MSGT USMC (Ret) & Earlene (CinCHouse)
2008 Winnebago Destination 39W
It is what it is, and then it is what you make of it.