I believe Grant Fidelity is the current distributor but Ian Grant is quite ill so not sure how much support you will get there. Worth a try. However, I'd go to the GF forum over at AudioKarma for help.
It's actually an incredibly simple process. You need a 1/4" phono plug with two leads coming off of it so you can connect your voltmeter. Adjust to 4.5V. 4.8V would be OK too, but I would advise against going higher than that.