I located some beads (India) that are as close a match as I think I can get. I was very pleasantly surprised that I found them, actually! I found some 2.5 mm sterling disks that look OK in the repair. I had to add some links that are not perfect, and my wire-wrapping is far from professional-level. However the replacement of the three missing beads looks OK from a distance. They are the group of three "Hail Mary" beads in the part of the rosary just above the crucifix.

I plan to re-do the repair if I get better parts and better skill with the wire work.

Note - the purchase of the rosary with 3 beads missing was a blunder on my part since I didn't study the description carefully enough to realize there were 3 beads missing...