I originally bought my Steinberger XL2A, used, in the late 1980s when they were falling out of style, for precisely this sort of thing.
I don't travel as much for my day job as I used to, so what I do now, whether it's a long working trip or a long vacation, is pack my little Vox AMPlug headphone amp, a pair of semi-decent earbuds, and a mini stereo patch cable. I've been very successful at borrowing or renting a basic practice bass wherever I've gone.
One time, on one of the Hawaiian islands, I walked into the only music store in the area and asked if they had a second-hand bass they'd be willing to sell me, with the understanding that I'd sell it back to them a week later, for some small and to-be-negotiated-in-advance loss. They then said "oh, you want to do a rental", and I said, yes, but you don't do rentals, and the manager said, essentially, "we do now", and let me rent it for something like $30 for the week. For a few trips a year, that beats schlepping and worrying about my own bass when I fly. In your case, if you're really on the road all the time, your uBass approach of is probably a good one.