I just used a regular Santa suit and modified it for him. I have plans to extend it under the saddle, over his rear and up over his neck for next year!
Whenever we looked at him, we kept cracking up and he'd look at us like "Whaaaattt?????! Haven't you ever seen a horse in a Santa suit before! Get a life......" Funny thing was, the other horses were wearing antlers and didn't even look at each other twice but when one of the dad's took the antlers and stuck them on his head, then all the horses started spooking at him! Who knows what goes on in their minds