hooking up a travel trailer from the trailer's rear

I bet you could succeed with the type of manual dolly just posted to provide some form of "steering" / guidance. Then, use your vehicle front (or otherwise) to "nudge" it forward using some old tires as a "buffer" between the two. It doesn't need speed so it likely doesn't have to be anything "big"... just needs to align well with the bumpers. Of course, have your blocks ready... :-)

If your bumper needs some "help" taking the "load", strap a 2X6 to it to distribute some of the "forces".