Yeah they look like drywall anchors but not.
The one I saw is kind of like the one you picture but has very rounded edges.
They sell them in Europe (somehwhere) I wish I had taken a picture of them. A few shapers use them to find the best footstrap area with out having to epoxy inserts like you did. Once instal it look like is not even there.
Comments on your set up. What I saw pro riders doing is double chiken straps but in an angle. Which I think is a lot better for downwind positionand there way space out even more than what you did.
It help a lot for downwind angle and when overpowerd.
I really dont want to have to cut, add, and insert stuff. It is so simple to drill, epoxy and screw this things.
Thanks for the help. I will keep looking until I finally hit the right person for these. I have email a lot of board builders in europe to see if the know what i am talking about.