Sorry, I don't have a good source for buying them COT, but you an always have a gear burned via wire EDM. It should be roughly $50 to have a gear cut depending on the material and how busy the source is. As to sources for either cutting the gears or wire burning them, Detroit has 100's of them. If you can't find one in your area, give me a PM.
By the way, trying to find a 19T gear for you, I came across
THIS file from Boston Gear that I think has a pretty good intro to gear terminology.
Check it out.
Joe J.