If you can stand the foul stench, perhaps going out the third-base gate to the smokers' area might work? You do risk noise from sirens and the like.
Or if you frequently have to take calls on the road, such as in your car, perhaps a noise-cancelling Bluetooth earpiece could work. I have one for when I drive my wife's car or our convertible (my sedan has a built-in Bluetooth system) and it works really well—I once called my father from the convertible when I was driving 75 mph with the top down in the I-395 express lanes and the noise-cancellation was effective enough that he didn't believe I was in the car until I honked the horn at some idiot. I have no idea how effective such a device would be at a game, though I'm sure if you remained in the stands it would be obvious where you were.
