Well, posting the question seems to have prompted me to figure this out ...
Using the provided demo diagram, I added a line to the fin function:
fin = function () { this.flag = rgpopup(this.bar.x, this.bar.y, this.bar.value || "0").insertBefore(this); this.attr({href: "http://myurl.com/"+this.bar.x+"/"+this.bar.y+"/"+this.bar.value}); },
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