Mine is also on a regular true type, but the narrow version is getting easier to find and in stock at Sideshow and toy Anxiety (at least the last time I looked) so if you want the narrow, it won't be too terribly expensive.
Well, you could always put it in boiling water and try to pop it off. (The infamous "boil and pop" method).
Or you could check eBay or Toy Anxiety for a Clone Trooper Kenobi head, those fit a long TrueType neck post perfectly, and are exactly the same as the EP2 heads as far as I know (except for the fact the EP2 has a sculpted neck, while the Clone Trooper Kenobi head does not have a neck at all)
if you've already painted the head, and are afraid of dunking it into hot water, a hair dryer with the heat applied to the neck seal (with some material to protect the bonce), works too.