As odd as this sounds, these people may be able to make you a spring:
Antique Phonograph Supply (antiquephono.com)
The owners, Dennis & Patti, are very nice people and have made custom springs for me to fit all kinds of phonographs and not-at-all-phono-related items since the 1980's. Actually, if I remember correctly the return spring on my Rockwell drill press came from them. Dennis is a top of the line machinist, so a good conversation can certainly be had!
Plan B- A clock repair part supplier, such as Merritt or S. LaRose may have a 'close enough' spring. (I could not find the URLs or phone numbers tonight. My computer is bogging down terribly right now.)
Neat Tools You Found! Enjoy using them!
Paul