Yes m_c it does, but the closest i can find is the Easychange toolholder from Coventry.
The diameter on top is 22mm, and yes i think it`s a standard pull stud.
There`s 2 ways i can solve this. One is to send my measurements to Coventry Toolholders for confirmation and ask if they have the Version with the groove in the top flange.
And if the dimensions are the same but without the groove, it should be fairly simple to fix that with my lathe.
The second solution is to make them myself in the lathe. but that one is manual so far(which will produce a lot work work).
I got a bunch of the standard endmill holders with sidelock that i could sell out since i like the onces for collet chucks better.