The shop manual refers to two springs, one on each side. If you only put one on, the runners will tend to bind up.
If you only have one spring, you should be able to find a matching one at a decent hardware store. If you don't have one, maybe a helpful 'bolter will help out with some measurements. (Hint, Hint. I need those as well.)
the end to end measure is approx 12 inches , i tried home depot last night and you know how that goes , will have to try a few mom and pop stores i seem to have better luck there sometimes . Auto parts stores are a joke if they cant punch in a number they cant help either