Pole-ish thoughts
While it's been a couple decades since I built a spinn. pole for our prior boat, I still have the hand-and-wrench swager I bought to do the bridles and trip lines.
If you have access to a bench mounted one in a chandlers that would be better in some ways, and less so in others.
I bought an alum. tube from a local metals supply house and like others here found a deal on the ends for it.
One other thing I did (and have done again when rebuilding the pole for our present boat) is to stuff the inside with foam peanuts. If you lose it over the side in a busy mark rounding at least it will float until you circle back for it!
Cheers,
Loren