Check with Colt and if they will no longer work on a gun that old, you can have it repaired at Cylinder & Slide Shop or Frank Glenn.
Cylinder & Slide is a nationally known custom shop. The work is top of the line, but prices are high and due to work load, turnaround may be slow.
http://www.cylinder-slide.com/
Frank Glenn has a national rep for Colt work. I don't know about his prices or turnaround times.
http://www.glenncustom.com/