More power (literally) for the HP-41, follow-up.

[Chr Yoko]

LiIon transportation is now carefully checked and needs to follow UN rules.

Post might reject your battery module as it is not self contained at all.
ie: Your pouch should be inside a closed container at least.
Can't you find a metallic small box to ship it into ?
Or 3D print a bespoke sealed box ?

The real issue is that the pouch is exposed and could be damaged during transportation.
It could get thermal runaway then and put fire to the truck , train , plane !