I have never understood why the plate is threaded. Other than the center hole, I don't see any advantage.
Like in this case, it just creates more work and requires a special fastener. It all significantly adds to the cost and complexity. Maybe someone can clue me in. My plates just use holes.
I'd drill the holes out and use regular bolts.
Same thing with risers. Just use a longer bolt and a hollow bushing or piece of tube. Cut up an old marker.