First, check with APHIS (USDA) for any restrictions about exporting seeds. Transporting plants and plant parts tends to be rather highly restricted for any number of reasons but seeds usually have less issues than other cuttings or plugs, etc. But there is still generally a lot of paperwork that needs to be filled out or filed.

It is actually rather late in the season to be shipping hellebore seeds. For the best germination, they should be sown as soon as ripe - in late spring or early summer. The biggest issue is the seeds drying out. Shipping in plastic snack bags with a few air holes pricked in is close to ideal. Personally I would lay the seeds between pieces of toilet paper or paper towels and then slide into a plastic bag (with air holes). That would keep the seeds from clumping together and the potential of rotting each other and the air holes would provide needed oxygen. Wrapping in tinfoil can work as well.