http://chrisking.com/headsets/hds_gnut
this is grip nut, its for threaded forks, I have one on My Bike Friday..

you have a threadless fork , that is the appropriate piece for those.
http://chrisking.com/headsets/hds_nts

Griplock cap? IDK. see none mentioned here? http://chrisking.com/tech/tech_headsets