Somewhat related here - But I've milled/drilled many a motorcycle case to accept standard roller bearings if that's what you're after . Some metrics are real hard to find especially the OD. so usually milling out the hole say a half a mm or so to the next size allows a $10 open double roller vs a $35 OE ball (Montesa or Silver Pidgeon engine ) If the original bearing is available why reinvent the wheel for thousands like the last post stated??