For true portability I’d suggest something shorter scale.
Personally I always found short scales a compromise, not always that much smaller and not as full sounding as a long scale, but not without charm.
In this case I decided to try a half scale bass, which might not seem to make any sense, but bear with me. Being half scale you can use regular strings, normal tuning but an octave up, which sounds very full.
You can always then add an octaver, which gives a really great sound, almost a signature sound on its own. I feel that sounds much better than a normally tuned short scale.
Then it becomes a fun instrument in its own right, which opens up new ideas and ways of making basslines.
They are made by a few companies and it seems lots of luthiers are open to the idea, too. Mine is a Wingbass (designed by the owner to fit into hand luggage) but I’ve seen some great looking ones on here from Stradi (see also his Facebook page), Sting was recently seen with a Mayones, but Mayones won’t tell me anything or even give me a response.
Another advantage is that you keep the same spacing as a normal bass, same strings (think I went one sub level heavier, Elixir light instead of super light) and you won’t want to put it down.
Worth considering perhaps - I’m sure a UK based company can rustle one up for you at a relatively low cost, it needn’t be too fancy but the temptation to fill it with gadgets was too great for me lol
I’m in York if you’d like to try mine