Your story sounds almost identical to ours when we owned our Springdale camper. About the 7th year of ownership, hail pelted the TT. 3 roof vent covers were beaten out. I duck taped them to create a cover. One over the bed broke out completely, mattress was soaked through and through.
At the same time, the hail broke out the very brittle and frail fan blades in the vent in the bathroom. When I touched one of the remaining blades, it just crumbled.
I took the lazy route and took it to a nearby dealer and they replaced all 3 vent covers with new ones. They also could not match the actual fan blade, so they just put in a whole new motor with a new fan blade. It worked great!
We also had them install air-maxx style covers over the roof vents in the event we'd ever get hit with hail again. We kept the camper another year and a half, almost 2 years after then, and finally traded for new one. First thing I had the dealer do, before we even hitched to the truck that very first time, was to put covers over all the vents. Best thing we could have done!
Actually, the cost was surprising reasonable for the entire repair of fan, covers, and hoods, parts, labor and everything. As I remember, labor and everything was just around $200. I would have spent $200 in fuel lone just driving around trying to find that fan replacement! I thought I got a good deal. I'd do it again that way if it happened again.
If you're going to fix it yourself, and unable to find matching parts from a good RV dealer, you're next best option is surfing the Internet, or visiting RV salvage yards.
EDIT: As Bumpy also said above, the Max Air vent covers is a good alternate replacement. You can install those yourself, if you've got the time!
