Are you sure it's the switch? Do the hazards all work? Don't forget (if I recall correctly) the indicators are powered via the hazard switch.
I think they were ex. Land rover. You can get them and the old ford transit types for earlier cars from John Worrall at HoE.
There is no spring as such just a copper contact for the connection. Should be say to remove (two screws) and a connector block for the wiring loom.
Perhaps just some contact cleaner or a bit of bending of the contact is all that's needed.
