I am not aware of any place that does calibration on ball gauges. However, I am curious...what make and model of ball gauge do you have that seems to be out of calibration? Is it possible that you have a cheap gauge that never was calibrated properly to begin with? I have never heard of a gauge being out of calibration - just broken and not working properly.
As an FYI, Molten and Mikasa have digital electronic gauges available that cost $60 and $40 respectively while Molten and Tandem have inexpensive dial-type gauges with air release valves for $15 each. Any of them are available from
Roof Sportswear in Southern California.
Good luck, I hope that you find something that gives you the results that you want.