i made it up in my head so i cant tell you where to find something that looks like mine lol but i would recommend buying just a solid piece of aluminum in the diameter you want and then go to someone who owns a lathe and start playing.
if you dont know anybody with a lathe. if i find time to do it. i can lathe a freehand design for you if you gave me the diameter of the knot and depth of the knotbase and the lenght of the handle. and then you can just epoxy the handle on your brush. i would do this for material cost.