Pete,
Call the local music stores. They still sell tube gear and they almost always have someone that repair(s) the guitar amps, etc. They will usually repair or calibrate tube testers. There is another place that started out selling used gear but they now carry new gear. I believe the name is Hi-Tech. When I lived there they would work on tube gear, etc. And there is Angela Instruments out past Laurel,MD. He may be able to assist you. Good luck! Lastly, search Ebay for tube tester calibration. There is a place in Wilmington, N.C. that does just that. I found them last week while searching for a B&K tube tester.
