For a mast,
Buy a piece of AL tube (.060 wall will do). Make and hammer wood plugs
in both ends and the pick one end to drill through sideways to run in an
eyebolt to hold the halyard block.

Not having much luck finding anybody who has 2-3/8" diameter aluminum
tubing in 12' lengths. It seems to jump from 2" to 2-1/2" to 3" every
place I've checked so far. Do you know of anyone who would have it in
that diameter and length, who would charge well under $85 for it (if
I'm going to pay that much, even including shipping, I may as well buy
the factory part).