www.google.com/webhp?q=h18%20topcap%20fork
yeah thanks, but that only answered half my question =P
but it reminded me, that the tree one might work (still available in some stores)
the cult kinda scares me off with the square whole in the top? guess it has a hex fitting inside somewhere.
to my surprise i found an old wtp top-bolt in my old-parts-bin that fits.
still confused, if i still need the forks steer-tube "protection" insert with the race forks, or if it was for use with the elementary stem only - anybody remembers?
guess it was something about the forks steer-tube thickness that made the insert cap above the stem necessary.