I recently made a new whisker pole as the one we had been using was too short and the end fittings were not sturdy enough.
The starting point was to find some good automatic pole ends for a reasonable price.

These came from Nautos USA and fit inside a 2" tube. Landed, they were about $100 each but are beautifully engineered.
The next challenge was to find 2" tube or face getting them turned down to fit 50mm tube. Luckily, Laser top mast sections are 2" diameter and sacrificing two made it easy to make up the 4.1m length required.
Now, how to join them? Finding an old windsurfer mast, we slid the 2" tube over the tapered fibreglass mast until a snug fit was reached. That 500mm section was cut and used as an internal sleeve. Epoxy, rivets, tape over the join and bingo! A new whisker pole for $200.