Quickest recourse for parts would be directly thru HWH. You could also try a search using the part number. For a cylinder rebuild I would first search locally for hydraulic repair shop over send it back to HWH. Might be a few dollars less plus the cost of shipping a couple pounds of steel cross country.
A lot of the stuff bolted to a coach is actually used in other industries rather than being exclusive to the RVs so find alternative supplies over the OEM is possible you just have to spend the time search and thinking outside the RV box.