best practice - reconnecting dynamo field solid wire

[JonE]

I've got broken wire running into the fields. It is solid copper. I can overlap it by a few mm and resolder (to the eye which connects onto the 3rd brush), but that alters its original length. Are the any forms of insert copper tube that would repair this more strongly than a simple solder join?

I'm also head scratching over how to get an insulated sleeve in this sort of position, where you can't get the shrink far enough away from the area to allow it work. How do people re-insulate in such places?