Hey Norm... I would say the best place to get them would be straight from Tim B. I keep meaning to order endcaps for my Gem. I destroyed both of mine on my stupid rocky beach.
Tim is probably my best source, although they are not for my Gemini. I want to replace the APA stand-off holders Matt used on the Synthesis. I am not happy how they work.
@ Rob: I have some vinyl end caps that will fit the nocks on your Gem. I'll send you a pair when I mail your straps for the AVFFF "trick challenge".

Best to replace them before you break the nocks on that rocky beach.
@ CA Ike: Can you give me a link? JACO's...I guess I'm not aware.
@ Steve: Tim and J.O.E. are both top notch and I'm lucky to have both of their kites. They both use the same type roll-bar holders, except J.O.E. (Mark) adds an addictional piece.