Wow, I was checking up on some gear stuff for my own team and decided to look around a bit. I checked all the sites that Cory listed, McMaster had the 20pa stuff like David said he had, sdp-si had some other stuff too. I looked around at Boston Gear and Martin Sprocket & Gear, they came up fairly blank too.
WM Berg makes 20pa of assorted pitches.
If you find this stuff, i'm guessing it's gonna run you quite a price. You may want to start looking at some other solutions here (maybe 3, .5" face gears all lined up?) It's risky, but it's not looking good.