I need to repair a drawer in a Ram self assembly kitchen now 23 yrs old?

I need to repair a drawer in a Ram self assembly kitchen now 23 yrs old. Difficult to describe this exactly. 1 drawer of 8 is suffering fatigue and its moulded plastic framework has began to split. Drawer keeps slipping off guide rail as a result. Could replace plastic frame but can't seem to locate any suitable replacement though. Unit made by Ram - good quality - apart from this niggle.