Simon
I would consider carbon fibre. New carbon ready-made

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is expensive but you can make one up yourself from a bare tube and it would probably be cheaper than having stainless fabricated. If you belong to a sailing club with a half-competitive Laser/ILCA fleet it would be worth asking around if anyone has broken their carbon top mast; many windsurfer masts are also the same diameter. The advantage is that you can then get standard end plugs, around £7 each.
I got an old windsurfer mast, put two ILCA end plugs on it and epoxied dyneema onto the end to take the low friction ring for the downhaul. I lash it onto the bow roller with 10mm dyneema offcut from the main halyard, the back end lashes to the windlass where the deck is strong. Of course you could have your stainless guy make up smart fittings and a stem head hoop if you prefer, but being a cheapskate I am happy with my lash-up. It only takes five minutes and lashes onto the stanchions afterwards leaving the foredeck and bow roller clear.
Hope that helps
Peter

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Peter Dann
Blue Moon 325/32