It's the inside of a solid golf ball they come in all colors. I drilled a 1" hole in the ball on my drill press . I used a cheap spade bit. I cut off the end of the diggers plastic handle with my pocket knife. I then glued the ball on to the metal digger shaft, using construction glue. You can leave it looking like a golf ball and are done.
I trimmed off the outer white cover but you don't have to. I wood carve and it takes a pretty sharp knife to get the cover off. It will work fine it you just leave the cover on it will just look like golf ball. Here's one of my balls.