I called them the other day and they said that they discontinued the trim that was made for the Mark 8. There wasn't enough demand and they would have to make enough for six years to make it worth while so they discontinued it.
I too was looking at HR018C, maybe HR069C except this one has a point instead of smooth. HR018C would be the closest.
What about the black portion on the edges, did you trim it off or what? Do you have a close-up of it so I can see how it turned out? This could save me $6 for a 6 inch sample.