Welcome from Urbana, IL...
You mentioned 3 different vehicles. What are they?
Check out this link for the 2012 Dinghy Towing Guide by Motorhome
Downloadable Dinghy Guides | MotorHome Magazine
This one is free but earlier back editions do have some small fees. You would need the proper year for the vehicles you have to determine if they are towable. It will give you some ideas to start with including restrictions and special information on toads.
I don't know of any special place to find vehicles for sale that are already set up. I have seen a couple references from others that might help.
Don, Sandee & GSD Zeus. Gardian Wings earned are GSDs Gunny (7/11/15) & Thor (5/5/15)
2006 DSDP 4320, Spartan MM IFS, 2013 CR-V, Blue Ox Avail, SMI AF1, Samsung 197R Refer.