Ahh, a dilemma many of us faced when we first got a motorized RV. Nothing you own is flat towable as is, don't want to buy a new vehicle, nor do you want to modify what you have. Been there. :)
If getting another vehicle or modifying an existing one to flat tow is definitely not an option, my recommendation is this: Get you a tow dolly or flatbed trailer, and use (tolerate) that for the time being to tow one of the vehicles you have.
Then, when it comes time that you'd be replacing, trading one of your vehicles anyway, trade it for one that is flat towable as is. You can then sell the dolly or flatbed trailer and use the $$ you get back out of it to help pay for a tow bar, base plates, etc. to get your new vehicle set up to tow.
Thats what I WISH we would have done, haha. We started out with the dolly, did not like it, sold it, used the $$ to modify an existing vehicle to tow (added a lube pump). That lasted about a year, 'til we got to where we just didn't trust the lube pump, so chose to trade our other vehicle that was getting old (my everyday driver) in for one that is flat towable as is (Ford Fusion hybrid).
In hindsight, I wish we would have just toughed it out with the dolly until trading my vehicle, and never put the lube pump in DW's vehicle (Kia Sedona van). Would have saved a lot of $$ in the long run, haha. :)