Hi John,

the first place you can check (locally) would be Jouets Molard, Jouets Bollet or Reve de Gosse (Carouge). Maerklin Switzerland has an authorized service agent. You can contact them at
Herr Alexander Stelzer
Telefon: 056 / 667 3663
Telefax: 056 / 667 4664
E-Mail: service(at)maerklin.ch

You can also contact service(at)maerklin.de to see if your locomotive can be repaired at the factory (Goeppingen) in Germany.

For parts for older models, I recommend the following sites:
CH: http://www.buco-hag-maerklin-ersatzteile.ch
DE: https://www.ritter-restaurationen.de

You can also get in contact with Jacques Vuyes through the forum. He has a reputation of being quite well versed in maintenance and upgrades to older models.

I hope that this information is of help to you.

Regards from the rest of la Francophonie where we say soixante-dix and quatre-vingt instead of septante and octante.

Mike C