There is a company called Northwest Short Line that caters to the Model Railroad industry making gears for locomotives of all scales. They make a lot more then that actually but I know for a fact they will cut gears but I am not sure they have ever been approached before to cut gears for a different hobby. They probably have. If you need something replaced like this, might not hurt to at least get in contact with them and see what they say. Even better if you get a bunch of guys that need this part together to make it worth the while.
What this gear really needs is to be press pinned to a shaft similiar to whats done above, but to the shaft instead. Soldering or brazing it appearently doesnt hold the gear tight on the shaft enough to hold for long periods of time.
Just a thought.