What a handsome little guy! Of course, Momma's not bad looking, either!
Minimule, there's always AI
The only problem I see is, how big would the baby grow to be? I've heard it's usually about halfway between the parents, although I know mules often get a bit bigger. By my math, Kilroy x your Paint mare is only about 12 hands, give or take a little. While I've no doubt a 12, 13 hand mule could be strong enough to carry most men, it might look a little funny!