A good gunsmith will have springs. When I started messing with guns, I bought an assortment of long springs from Brownells... they can in about 12" runs with a dozen or so sizes... just clip off what you need. I have found that a great resource!
http://www.brownells.com/aspx/ns/store/ProductDetail.aspx?p=85&title=GENERAL+USE+SPRINGS
http://www.brownells.com/aspx/ns/store/ProductDetail.aspx?p=85&title=GENERAL+USE+SPRINGS