I have bought springs from Eaton and Jim Carter. Eaton used to have very good prices but they are expensive now.

I had to be careful to ask Eaton to use the original-style "leaf binders" because they normally use a metal band over a piece of rubber to clamp the ends of the springs together. If the appearance/composition of the spring clamps/clips are important to you, you might want to ask if they match the original.

Also, you might want to ask if new pivot bushings are provided with the springs (if that is important to you).