What's so special about the these gears, that you can't just buy some of the shelf ones, and modify them?

Anything steel is more likely to of been hobbed, which can still leave marks.

Nobody is quoting because it sounds like a quite time consuming and fiddly job, so it's probably not even worth their time quoting.
Rather than use a long bit, depending on quantity, you could make a jig, so you machine one side, then flip it, and machine the other side.