Jeff,
I believe the geometry of a single round over bit, as you have sketched it, is impossible. Beading bits can only work on one plane & each bead on a round over would lie on a different plane. The only work around that I can visualize would be to cut a regular round over & then use a scratch stock to shape each individual bead. This would be a tedious operation that would require a different set-up for each bead, something that I would only attempt if I had a commission to repair a valuable antique for someone who had deep pockets.
Sorry I couldn't be more help.
Paul