Jeanie and I toured Mark's (JPnAZ) new Lance 865 at OX, as it was the heir apparent to my old Lance 165-s and I can report I was very impressed and happy to see Lance has continued to upgrade their short and narrow 8'6" platform. Amazing what 15 years newer will get you. His is slightly heavier due to his air conditioner. My old 165-s with no AC weighs 1845 pounds, wet (18 gal. fresh/3 gal. hot/ full tank of propane).
Only a few mfgrs. offer this lower height ( 6'4" ceiling), 86" wide, xtra cab/N/S queen platform. Since we own one, of course, we think it's good enough.
You have not disclosed what truck you are thinking about using with this elusive camper. we don't need a brand, only a class or size. Mark's and mine are for a 6-1/2' short bed.
I'll have to agree that smaller hard sides are, it seems, difficult to obtain. The 10 to 11-1/2 footers are easy to find. Some have had good luck at CrankyApe.com
It's good that you are doing due diligence. This is a big decision.
regards, as always, jefe