Call Tony at Azusa engineering. http://www.azusaeng.com/
They stock pretty much any sprocket blank except the exact ones you actually need
They can get pretty close though and can usually find a compromise. It mainly has to do with how their machines are set up. You'll probably have to get custom and do your own bore and bolt circles. As far as I know, they can do from 20T up in #219 but they all are a .998" bore. I think they'd make anything for the right price but if you stick with stock cut sprockets and modify the centers yourself, it's a lot cheaper! It's the best supplier I've found and Tony seems like a very nice guy.
Also, RK makes some sweet o-ring #219 chain. You have to buy a special tool to work with it because there aren't master links but it's neat stuff.
Your build is flat out inspiring. I'd love to come down there and ride with you guys once I build something to ride that will keep up and be worthy of the company! If there's anything I can do to help, let me know!