Seal Case

If you have the seal case, there is a market in Sunyshore city that is separate from the Pokemart, a vendor there will sell a variety of pokeseals that will differ every day of the week. They are $50 to $100 each.

To get the Seal case, you must go to the ruins in Solaceon town, and talk to a small boy that is inside the ruins. When you finish talking to him, he will leave the ruins and go to his house, so follow him there, go inside, and talk to him again. He will say something about the ruins, and then the boy will hand the seal case over to you, so now you can carry more seals. Later on in the game, you may find various seals laying around, but the true seal shop is in the city of the last gym leader, SunyShore City. As soon as you enter Suny shore City, you should see a small building to the left of you, go in there, that is the Seal shop. Once you buy all the selas that you want, you will have to go to the Pokemon center to attach the Pokeseals, to the Pokeballs. Click on the PC, and then you will see the Poke Seals option, the rest is very easy to figure out.

There is a store in Sunyshore City that sells them.

There is also another way to get seal's,
Go back to the ruin's and cach as much Unknown's as you can,
Then show the boy who give's you the seal case all your Unknown's,
Then for every Unknown you show the boy you will get a new seal.
Like if you show him a Unknown A then the boy will give you a seal which look's
Like a A.

There is a mart in sunshore city that sells different seals everyday

You can get seals from the seal shop in sunnyshore city and you can also get the alphabet seals by taking the unown Pokemon and showing them to the little boy in the house near the solocean ruins.