Ash - Tanner moulds in the UK will make any size you want.
The name of the outfit has changed, since Jeff passed, but the lad is running the business. Moulds are CNC turned (I think) and are made of brass. They fit standard handles. I have 5 sets of these mould blocks & use the pliers-type wire strippers with little cut-outs for trimming the sprues - cut in part way and twist the ball - off comes the sprue and leaves the ball virtually round (with some practice).

https://www.ballmoulds.com/