Cab top lights - '66 C20

[Railroadman]

I'm nowhere near ready to deal with this part of the project, but will ask now to plan ahead. Two questions re rooftop running lights.

1. Who makes a replacement? I could probably get the paint off the chrome, but would at a minimum need the gasket they sit on and the lenses.

2. How does one go about replacing wiring? The 5 lights become 1 tan wire behind the driver's left shoulder, but I can't see any way to access where each one merges up above. I REALLY don't want to go removing welds etc but maybe that's the only answer? I'm afraid to pull too hard on one to see if there is enough slack, but guess I need to try.