There is nothing unique about the cabinets - you just buy a size/type that fits, or have a cabinet shop make the size & shape you want. They screw to the wall or floor or another cabinet. On the walls you have to locate and screw into a structural member that can support the weight. Just screwing into paneling won't last at all.
You could probably order an existing production size from Jayco's cabinet shop, but chances are it would take several months to get onto their work queue. Their priority is to build for new construction. Maybe a replacement door wouldn't be too long, though. However, most any competent cabinet shop could match the style and coloring. That's what they do...
Crow's suggestion about RV salvage yards also has good potential. There is a list of RV salvage sources in the RESOURCES section of this site. Click the menu at http://www.rvforum.net/SMF_forum/index.php?action=Resources and select 'RV parts & salvage'