The original plug cap if its 214262, is still available from the Land Rover Series One Club, who have had some reproduced , not sure if they only supply members though. John Wearing and John Craddock is listing them as wellThe originals didn't have rubber skirts, they had plastic towers (with holes so dirt still got in) that had the plug connector and the HT leads screwed into the top of the tower. If you can find a set of those, it is trivial to make up HT leads to suit.
Yours
Vern
Original 2200 HT leads have the rubber skirts that you mention, so that they effectively seal the spark plugs.
NOS ones appear from time to time.