Depending on the condition, I carefully bend the roller retaining tab, remove the rollers and plastic pieces, and clean up the inner and outer sections (bead blast to remove rust if necessary). Then paint the pieces semi-gloss black, let dry and reassemble. (Use white lithium grease on the rollers.) The springs I dip in a metal blackening solution and them cook for a ten a full 10 minutes in a phosphoric acid bath at 180F. The seat mounting bolts should be phosphate and oil. Replacements "may" be available at AMK.
Jim