There are 2 other springs on the assembly, one is to make the release pull handle spring back in position, and one is for the clicker pawl. The release handle spring can be replaced with a small general purpose spring, and the clicker pawl spring best replacement in my opinion is a Irwin Tools vise-grip pliers spring which last I knew you can get for free from Irwin tools by mail, or buy online.
Neither one of these springs has anything to do with the pedal returning to position.
The release pull handle spring is easiest to see and replace.
For the clicker pawl spring I hooked the circular end of the vise-grip spring to the pawl inside the assembly near where the pawl sticks out through the little window. Then stretch it down and put the hook end of the spring on the belly of the assembly.