There are many choices for towable vehicles - see the Motorhome Magazine Dinghy Towing Guide
for a list of vehicles that require no mods to tow. And many more can be towed with some modifications, typically a transmission lube pump or a drive shaft disconnect. Both of those will run upwards of $1000 (installed), though. Might be worth checking into one of those mods for your existing vehicles, though.
In general, front drive automatics will require the addition of a transmission lube pump, but there are some exceptions, e.g. the GM Lambda family (Acadia, Traverse, Enclave & Outlook).
4WD vehicles that have a neutral in the transfer case are nearly always towable. AWD mostly are not, but once again, there are exceptions.
You may find this Dinghy Towing Basics
article helpful as well.
If you can find a Suzuki Grand Vitara or Chevy Tracker 4-door 4WD SUV, that would be an excellent choice at a moderate price. A Honda CRV is also a great small toad, but likely to cost more than the other two. Older Honda Accords and Civics, most Jeeps, and most Saturns are also good bets, but always verify towability before buying.