There really isn't any stores in the Olympia Washington area.
If you have a extra couple hours there are several 40 miles or so up I-5.
First I would recommend is in Tukwilla WA.-Oceans By Design
Second is about 10-12 minutes further north on I-405- Barrier Reef
Third another 20 minutes north in Belevue- Saltwater City
Agreed, there is a few by Greenlake too, one is The Fish Store and the other is up by 105th and Aurora called Little Amazon. I hit both of them up when I have time while in Seattle.