Thank you for the reply.
Your idea of using magnets or some other form of adhesive to fix the beads (whether real or painted) is a good one. I forgot to mention, however, that the beads are the product that this little video is supposed to sell: expensive beads from a luxury jeweler. So, of course, we can't glue things to them or even recreate them by painting ball bearing, etc.
No, the more I think about this video the more it becomes clear that this particular idea can't be carried out as envisioned by the client, with the budget and the time we have. The best solution would be to use traditional stop-motion animation (also expensive, since it is so time-consuming) and do it frame by frame in two or three shots of a few seconds (and appropriate music and sound-effects).
I'll run it all with the client once we have something more concrete in mind, and we'll go from there ... which will be nowhere probably 'cause this is not going to be cheap. Lots of people have all sorts of ideas for "fun videos" until they realize that few are every simple and none are cheap.
Thanks again.