UPDATE: Yesterday evening I went to the music store and bought a .022" steel guitar spring. It's a little smaller than the .024" original. Later in the evening I fashioned and installed a home-made omega spring. It works, sort of. It was fairly easy to duplicate the shape using miniature needle nose pliers. BUT, the spring I made is not a strong as the original spring, so the homemade spring does not push the lock bar as far forward as the remaining original spring. I plan to go to the hobby store and get a bigger spring and try that out.
There's a big HOWEVER disclosure that goes with this. There's an instrument repairman at the music store. He took a look at the broken omega spring, and played with it a little. He then said, "this is strong spring. You can't make a replacement by just bending a guitar string into the same shape. This spring was heat treated AFTER IT WAS BENT INTO THE OMEGA SHAPE." I don't know for sure whether he knows his stuff, but it sounds plausible to me.
So, I might be wasting my time and setting myself up for lock failure. I'm going to make one more try, with larger music wire, and see how it works. I'll be extra careful with this 710 for a long while and give it a light spine whack test every so often.
I made the disclosure because I can't recommend others doing it after what the repairman said.
