Measure the size of the ball itself. The common choices are 2 1/4" aka 'mini' (the size of a cue-ball in pool), 3" 'midi' (juggling balls are supposedly often this size), and 4.5" aka 'maxi' (the same size as a 'candlepin' bowling ball).
I'm given to understand that Capcom Bowling is usually a 3" ball.
Once you know the size, you can order appropriate rollers, bearings, and balls from someone like Bob Roberts or RAM Controls. If the shafts are worn, you'll want to replace them, and you should think about doing the bearings as well. I didn't in my last rebuild, and I'm not sure that was wise.