I test-installed a return spring on one of the brake pedals, just to test the concept. Each unit is composed of:

1. A nylon collar (McMaster-Carr # 6389K625),
2. A 3" spring (# 9657K115),
3. A set-screw shaft-collar (# 9946K13).

I'll have to do some tests to see if I like the way the spring works. So far, I like the concept.