As I was shopping online for seaberry plants, I came across an ebay store that sells bush and tree seeds at a low price. They also combine shipping.
They are called myseeds.co and have a 99.3% rating.
I bought seaberry, goji berry, ground cherry, hops, and quince seeds for $10.62 (including shipping).
Here's the link to the store homepage:
http://stores.ebay.com/Nature-With-Love