I have guppies,
Hornwort, and sea-shells...
Shells-

(Note the CD for size reference.)
Here are some pictures of the small
Hornwort mat-

The large one and small one are $4 each... (Larger one has azolla and some algae in it so that explains the price...)
They grew in my soil-substrated aquarium with sunlight so it grew extremely dense...
Ideally, I would mail them in a medium priority box (since the small ones seem to be mishandled...)
I can try to cram one
Hornwort in a $5 priority box, but for best survival rate I'd reccomend the medium box for $10.
I also have male guppies for $1.00 each.... USA bred.

Could be feeders, but don't tell me. I have long-fin "fancy" and a few spade-tails...

(Yellow-tailed one there isn't for sale, but the others look the same only with red.)
Guppies are sent priority as well. Medium box only, with breather bags and sedative.