The Mini Maverick is seems to be one of the easier mini sets to find. He can be found on any of the three buckskin horses with a black mane and tail. I don’t have hard evidence to support it, but I wouldn't be surprised if he didn’t ship at times on the all buckskin colored horse. He shipped with a regular white mini hat. I recently purchased a mint Boxed Maverick set which had a brown Semi-Rearing horse. Fortunately, it came to me with a gold sticker to confirm the combination.

#562: Mini Maverick on Semi-Rearing horse with black mane & tail.