Jon at The Tube Store would be my recommendation. There is also Kevin Deal at Upscale Audio, as well as Andy at Vintage Tube. Both have a good reputation, but I have no direct experience with them to speak of. I can tell you I've been very pleased with Jon's service and products over the years. As far as NOS, his selection is sometimes limited. 6922's should not be a problem though. There are other dealers as well, and I'm sure others will chime in here.
For now here's The Tube Store's website.
Marco
For now here's The Tube Store's website.
Marco