Dan, I can't speak for the 250 as I have a 280 but have you looked in the toolbox as mine had a spare in there plus an extra spacer.
If you don't have a spare then you could turn up a round sleeve and just drill through the pair of gears for a pin rather than trying to form the integral key., it would do as a stop gap to give you feeds unless you are intending to do a lot of screw cutting of various pitches until the new one arrives.
I assume its the sintered one on the right
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