The ball detent caliber is 0.1875" and the BB caliber is 0.177 if I recall correctly. Plus most if not all BB's are copper clad, so the diameter of the steel ball is a little smaller yet. However, finding a 3/16" dia. steel ball and a 3/16" diameter compression spring should be easy. We don't have the spring length but Clausing will most likely either have some springs available or if not, be able to tell you the length and the wire gauge.
If it were mine, I would first procure the ball and spring and then partially assemble the handle/right eccentric, handle and shaft with the ball and spring and confirm that the detent dimple lines up properly with the detent ball. Then finish the assembly of the back gears and put a dial indicator on the smaller diameter between the gears and confirm that it breaks over center when engaged.