Over the years, Ive been able to get seeds to every continent using this method.
Corrugated plastic and Q-Tips
I get a for sale sign that is corrugated plastic then i plug one end with a Q-Tip, put in the seeds, then plug the other end with a qtip.
Place this in a standard sized envelope to mail. This bypasses most security scrutiny and protects the seeds against being crushed by the dreaded sorting rollers.
If i have to fill out a customs form, i just declare they are jewelry beads.
Never had a single problem with this method.
Plus, its super cheap both in materials and postage cost