Bonsai nurseries offer the best selection of bonsai trees and stock. Their stock plants tends to be grown for character and size. They have a great selection of trees in early development as well as more refined bonsai.
Your average nursery can also serve as a source of good stock, if you know what to look for, but they tend to favour stock of different characteristics then those that are favoured for bonsai.
Attending a club meeting can help you learn what to characteristics to look for in a plant you are looking to develop into a bonsai. If you are looking to buy a bonsai, or stock plant to develop into a bonsai, we suggest you start at your nearest bonsai nursery.