For several years I sold products at RV shows in Southern California and Q. Each year I spent time with the sales folks at Highway Products & Mountain Master booths. Both companies have well built units.
Unfortunately my current truck came with a Zip DEE unit which works fine for what I need. Otherwise, I would have ordered the units from Mountain Master only because I became better acquainted with one of the salesmen. Their generator box really dampens the sound and provides a secure spot for a portable generator.
For my first truck to tow a fifth wheel, I built a large storage box out of exterior plywood painted to protect from elements. The lid mounted to the front of the pickup bed with a long piano hinge. It was constructed using 1X2 for the frame with a 1/2" plywood insert. The lid was wide enough to rest on the pickup bed rails and I used a foam gasket to prevnt rain from getting into the storage. I created a plywood wall that fit just in front of the 5th wheel hitch. This created a storage area that encompassed the area from the front of the pickup bed to the wall I created and from side to side. Big enough to hold my generator, gas can and tool box plus other RV accessories.