These days you can get an used and working 45 CT1 for under 20 Euro. Almost for the same price you will get a CT3 or for little more (50-80 EUR) a 45-CT4 with second light. (Situation in Europe, don't know about the avaibility of used Metz flashes in the US.) So repair is economically only worth if it is just something to resolder inside the flash. In your case it seems it is the tube itself.
You could ask Metz directly. They respond fast and are very helpful.