Something adhesive in the groove where the bowl rests might keep it in place, like one of those felt spots used on the bottom of pottery to keep it from scratching the furniture, or a small patch of electrician's tape or something similar that is slightly adhesive on the top might keep it from skidding off. Or a postage stamp size piece of duct tape with half folded double, but with a sticky patch, might act as a back stop to hold the bowl in place. I think a simple low-tech fix like this might do the job.