If form follows function, look for a pre-2007 RAM 2500 4WD long bed Cummins (no soot bag or D.E.F. canister) and slide a new Lance 815 on the back. Why the Lance 815? It's the narrowest (86 inches without jacks), least tall (6 feet 4 inches inside), lightest (1842 pounds, wet) which will offer you the best chance when on a lonely desert track.
Your life will thank you for a good night's sleep, deleting all that crawling around at night and doing without, but include all the amenities to be self supporting no matter the weather, season or location. Depending on how young or tough you are, you will enjoy the fridge, furnace, good queen bed, fully stocked kitchen, table and seating for doing business, privacy, quietude, pumped water supply, grey tank, black tank or cassette toilet, wet bath with shower, toilet, mirror, and sink. We have immensely enjoyed having 200 watts of solar to power our stuff. After sleeping in our even smaller Lance 165-s for 235 nights over 18 years, my wife and I both agree that the camper offers the best sleep we ever get. I know several folks and couples who have made this a lifestyle living in one of these full time. For hauling space, a small enclosed utility trailer will offer all the space you need for your sales needs. Slap the company logo on there and it could be a tax write off. If you are only on the road some of the time, a truck camper offers a good platform for Layovering between clients, many times in their parking lot (with their permission, of course). The good news with a hard side is your ability to layover anywhere it's legal and not be too conspicuous as it doesn't change shape into what I call the 'camping mode'. Nothing hanging outside; nothing set up outside; looks like no one is home.
It's a function of age that we've graduated from six Jeeps, Toyota FJ-40 and FJ-55 with trailer, 1980 Scout Traveler (118" w.b.) with factory Nissan 3.3L turbo diesel, to a 2001.5 Dodge RAM to tow our jeeps to the trailhead. Now we're down to one 1999 XJ, one 2011 Jeep Grand Chero, one short bed Dodge pickup with the legendary Cummins engine and Lance 165-s Camper, and one 2007 Kioti 4WD, 3 cyl. 35 HP diesel tractor.
At least this is something to think about in your quest for a replacement, only if you are up for a paradigm shift.
jefe