In 2004, my 1994 Bounder tail light assembly had rusted out and was beyond repair. Only light that worked was the brake light. I'd spent several leisurely months driving around the countryside after buying that RV and occasionally I'd stop in at small out of the way RV dealers looking for a replacement. Well, one day, I stopped at a 'boat shop' of all places in Milton-Freewater Oregon. And darn if they didn't have the entire backup, running, brake light assembly, for my RV! Cost me $25.
The point is, there's almost always a replacement out there somewhere. And if you're able to limp along with what you have, searching out of the way places for RV parts is not only fun, it's sometimes rewarding.