That's cute, but sorry I've not seen anything like it. Maybe just knit a plain cup cozy and then skinny tubes to sew on for the arms (maybe I cord)? The hands would be a little more complicated but I bet you could do it.
I should never overestimate my basic arithmetic skills.
Like Grumpygrandma said. I don't think you're going to find an exact pattern for this anyway. Everybody's coffee cups are different sizes. I have one cup that's little and delicate and my other cups are so large you can fit two cups of coffee in them. I would suggest measuring your cup's height and width around, ignoring the handle. Most cozies I have seen have a small strap going under the cup handle with a button or velcro closure. The drumsticks would be knit flat, seamed up, stuffed, and sewn into the proper position. It's just a ribbed band on the top and bottom with a stockinette body. Think Rectangle and you should be able to do this. I have confidence in you!