A 3A should not have a screw through the ring. The early unobtanium rings were split and used a screw that ran between the halves; but the later ones that are available had no screw at all and the ring just snaps into place.
My experience has been that the tab has a tendency to bend rather than going into the clip, unless I turn the removal tool around backwards and slide it between the trim ring and the bulb retaining ring, to push the tab through the clip.
Can't help with the rivet, I bought mine from TRF and they came with the tab already installed.
One caution, though, be sure you get the hole for the tab and not the drain hole. The first pair of rings I got had the tab in the wrong place and would not fit. (TRF replaced them promptly with correct ones, though.)