I used an aluminum cigar tube, but drilled the holes
using my fingers. Do not go through both sides of
the tube. That way the burrs are only on the inside.
Nobody cares about burrs on the inside.
You might try some nylon stockings or fish tank
skimmer net, with some modification. Make a
little pouch out of the material.
How big is this 'travel' humi?
Chemyst