You can have an implant called "Suprelorin" its a chemical castration and last for 6mths, like a microchip under the skin that disperses over time.

Im currently using it very successfully with two males and an in season bitch. It will tell you if castration will work, if you like the effect it has on your dog, you can go for the permanent option when it wears off, if it doesnt help, you (or he) has lost nothing! It also appears not to change the dogs coat, nor have mine gained any weight.