I'm not sure what you should buy. I can tell you what I bought, though, when I was in a similar situation. I bought a removable neck Eminence. Its scale is maybe a half inch different than my upright, but feels pretty similar and is loud enough to hear in a hotel room unamplified without disturbing people in the other rooms. It fits in a hard shell golf club case and I've never had a problem checking it onto a plane nor had to pay any extra fees. The only issue with it for practicing, IMO, is that it takes about 30 to 45 minutes to break it down and pack it, and 30 to 45 minutes to set it back up, and a day for the strings to settle out, although I guess that time varies with the strings with some being better and others being worse. It's not an upright, but I usually bring it along if I'm going to be someplace for more than a couple of days and will have time to practice.
But, if I'm only going away for a couple of days, and expect to have quite a bit of down time to practice, I bring along my NS Design Omnibass. It's a short scale, solid body instrument. With the right strings and EQ, it sounds kind of like an upright, but not really. I use it on its end-pin stand. It's great for shorter trips because it will fit in the overhead compartment and requires no setup or breakdown other than taking it off its stand and folding the stand up. Again, it's loud enough for me to hear in a hotel room without disturbing anyone else. It takes me 30 minutes or so to adjust to the small scale, but it's not a big issue for me.
Both are bowable with an acceptable tone for practicing, IMO.
There might be better options out there. Both of these work well for me, and I don't expect to look to replace them.
Hope that helps. The greatest value I've found with the Omnibass is that it helps me maintain my callouses and intonation. The Eminence is similar but I use it for "sketchy" gigs where I'm unsure of the load in, and/or, I don't think my band leader will care. Most of my band leaders aren't very picky as long as there's a low diatonic pitch at the right moment. If reasonably possible, I'll chose my URB every time. I also use the Eminence every year for the Aebersold camp because it's just not quite reasonable to lug my URB to no-where Kentucky from LA. "No-where" because the airlines consider it so; I like Louisville, but it appears that not many people travel there. This year, I played a URB as often as I could snag one from someone. Got to play some great URBs and I got whacked a couple of times for it. I appreciate where they're coming from, but, I treated those URBs like my own infant - probably better than their owner.
