Welcome to iRV2.
I'm sure some of our full timing members will be along with ideas on brands that might work.
My last 5er, ( not a TH ) was the only 4 season unit that I'd owned , so here are a few things to look for.
Enclosed and heated tanks and drain valves.
A floor plan that is usable with the slides in , because when the temp gets way down , you may have to pull the slides in order to keep the interior temp comfortable.
Good luck with your search . and Safe Travels.