King Snakes work to some degree as they have a natural immunity to most venomous snakes and prey on other snakes.
Keeping one there may prove difficult though. I found a 5 foot one in the barn next to my pond and shortly thereafter found 13 snake eggs. I was able to hatch 3 of them out and ID them as King Snakes. They went right back to the pond and barn. I have only seen one copperhead on my property in the last 3 years. Haven't seen any since releasing the King snakes.
