A "bowl" is, roughly, a hemisphere that has its interior hollowed out. Do you see any of these in a bowling alley?
We obviously could start with an ordinary (new undrilled) bowling ball, cut it in half, and remove the core, leaving the outer shell. We get two bowling bowls that way, of course, although
we might want to make them from scratch with a thicker shell. They will be subjected to a lot of abuse, after all!
The bowling lanes are slippery, and allow even ordinary bowling balls to slide (especially obvious when little kids throw balls). Just set one of these bowls hollowed-side down, and push. For ease of pushing, use a shuffleboard stick.
When the bowl interacts with the pins, the action will be considerably different than when a ball is used. This is because the pins are widest at about the same place where a ball is widest, but a bowling bowl's widest place is at its base, where the pins are narrower. That makes it a bit tougher to cause all the pins to be knocked over --BUT the way the pins fall will be different, too. There will be a tendency for each one struck by the bowling bowl to fall over the top of the bowling bowl, instead of being pushed aside as by a ball. So likely more of them will be rolling around on the lane, hitting other pins. Obtaining a "strike" may not be so tough, after all.
Finally, the machinery in the back, of course, needs to be specially modified to be able return the bowls to the bowler. The ball-return trackway probably needs to be modified, too.