Here are two nurseries I've visited.
Japan Bonsai
Masahiro Furukawa
10813 SW Barbur Blvd.
Portland, OR
(503) 245-4346
Pre-Bonsai and Bonsai. Pots, Tools and supplies. Classes.
Koyama Nursery
Robert Guitron
koyamabonsai@hotmail.com
425 SE 3rd. #2020
Portland, OR 97214
By appointment (503) 232-0435
Pre-Bonsai and Bonsai. Pots, Tools and supplies. Classes.