Right, but since they are made in small quantity and specifically for this purpose, I am assuming that they are expensive - even before adding the international freight.

Tom Haberman did not reply to my request for a quote, so I tried to find an alternative and discovered that tubular telescopic fishing rod blanks are readily available here and relatively inexpensive. I prepared a few battens that worked well in light wind, but still have to be tried in heavier conditions. My main concern is their durability, especially if someone falls on the mainsail in a capsize, so I filled them with polyurethane foam, hoping that this will reduce their fragility.

They could also be reinforced with a carbon or glass sleeve, that can accomodate variable diameters, in which case they would work as lost male plugs, but I had to try the simplest solution first.