Welcome to the forum. For original interior light fixtures you likely will need to contact Thor for specific part numbers (unless the maker and part number are marked on the fixture you need to replace). Then ask your Dealer to order the part from Thor if you can't find the maker directly on the fixture. An “alternative but close”, if not exact replacement fixture, may be available from Command Electronics (look under interior menu); failing that try an RV wrecker. Someone else may have more specifics for you though. Good luck.
The Lights â€” Command Electronics