Have you called Steve Young at Pinball Resource? If you don’t already have a copy of the manual and schematics for your game you can order these as well.
http://www.pbresource.com/index.html

You probably want Gottlieb # A-284 Reset Torsion Spring which you can get from Steve Young's Pinball Resource in New York.

I found the part number in my hard copy of the Gottlieb 1960 Parts Catalog.

As the last two have said, call Steve at PBR 845-473-7114
Mondays are extremely busy when calling " Pinball Resource" so just take the busy signal in stride.

Here in Olympia, Washington, sometimes when we call we get a "Sorry your call did not go through" telephone company message instead of a busy signal. Don't worry, just keep trying.