My take on the replacement universal cap is self amalgamating tape. Satisfies all diameters. Manufacturing time 36hrs.
Cut 4 pieces, 5" plus one diameter in length.
Place 2 pieces neatly in the form of a cross.
Place 2 more pieces neatly in the form of a second cross.
Press down with a weight to let the amalgamating process take effect overnight.
Lightly apply silicone grease to the pole outside diameter.
Place one cross over the end of the pole. Fold the pieces down the sides of the pole.
Secure temporarily with a cable tie round the ends of the pieces.
Place the second cross on top of the first, rotated 45degrees from the first cross.
Again fold the pieces down the sides of the pole. This is a bit fiddly, you really need 4 hands.
Carefully position the pieces and again secure as above.
When satisfied with the positioning, fit 4 cable ties to hold the self amag together.
Leave overnight for more magic to occur.
After breakfast, remove the cable ties and apply a layer of insulating tape to the cap external diameter. It may be useful to apply a little super glue to the tail of the tape to make a permanent bond.
The first time of removing the cap it may be a little tight but it soon eases up. Apply a little silicone grease as necessary.
Carefully trim the cap diameter to the length required.
Fit a boot lace to stop your new cap getting adventure-lust beyond it’s station.