Running wiring up a solid mast

[Brigadoon]

I have a 30ft traditional cutter with a solid pine mast. She has port, starboard and stern navigation lights but no steaming light. I know that I should have a 'masthead' (or at least quite high) white light, but am unsure of the best way to run the wiring. I don't really want to run it up a shroud, as it will look tacky. Should I run a groove up the mast, and will this encourage rot, etc.

I've also considered an LED light with batteries, but then there are mounting and switching issues.

Any help appreciated.

(Apologies if this has already been asked, I can't get the search to work.)