Would RV manufacturer have extra accessories for purchase?

This would depend upon the manufacturer of the trailer or RV but many do supply their authorized service centers with parts. They will usually order these for their customers from the factory. Some centers have accessory shops in which they stock some of these parts for the rigs that they sell. Check with a dealer of your trailer and ask if they will order replacements for you. For my RV this can be done and others do this as well.