I went to You Tube and looked at the videos on there concerning the 2009 Dutchmen Northshore XRV 33 5th Wheel. I could not see those brackets on their trailers so would suspect that this is an add-on. The bracket looks like the one used on one of those retractable dryers or BBQ’s. I installed one of those dryers in the kitchen of a church and the bracket is exactly what you have mounted there. Take your measurements and go searching the web for something similar.
"We were not placed on this earth to see through one another, but rather to see one another through!"
2013 Timber Ridge, 2013 GMC Sierra 6.2 L