I have a method that I have used here in the US with great success. I use corrugated plastic (like they use for signs in the yard), paper coin holders, and a card. I cut out the plastic in a circle so it will fit in the coin holder. I put tape over one side of the corrugated plastic, put the seeds in the holes, then tape the other end. This goes in a coin holder and I staple the two sides, then cut 1/8" off the bottom. Finally I put one more coin holder around the other coin holder and staple the bottom. This is labeled and then I will put it in a card and staple the card around the seeds. I usually throw in some stickers with the card and mail it with a single stamp. Total it probably costs me $1 to mail 1 or 2 packs.