You can dry your sourdough to travel with it. Just pour a thin layer of
active culture onto wax paper and leave it to dry in a clean place. A
1/4" layer may take a week to dry thoroughly. When it's dry, grind it to
a powder. It will remain viable indefinitely. To reconstitute it, take
some (not all - save some to correct errors!) and add it to 1/2 C water
and 1/2 C flour. A quart mason jar works well for this purpose. Stir
well and put aside in a warm place for 24 hours. By that time you should
see alcohol on top. Add another half cup each of water and flour and
repeat. If the total volume in your jar gets too high (remember, once
it's active it will want to double) throw some out before you add the
water and flour.
With a few repetitions of this feeding you will have an active culture.
Ed Wood's book expresses concern about the potential difficulties of
carrying an unidentified white powder across international boundaries. I
would take this seriously. Ask the officials of the country you're
entering how to solve the problem.
Good luck.
Jay