If the problem was just the mismatched key....you could easily remedy that by milling one side of the key to fit in the gear keyway. If your gears are trashed, that's a whole different situation. I'm sure there are guys on this forum that could make those parts...I'm not one of them. I have toyed around with making gears but in all honesty I haven't been real pleased with the finished product. The worm gear might actually be the easy part. You would need to broach the slot through it to mount the drive key. The other gear would be a problem for me. You might get lucky and find a job shop that isn't real busy and can do it for a decent price. It's still not going to be cheap. You might want to post under Machine Accessories and ask if someone knows of a used machine parts dealer. I remember seeing different posts in the past where people suggested some places to find used lathe parts. The only place that comes to mind for me is Lost Creek Machine. I know they sometimes part out machines. You can find them if you do a google search. Good Luck.
Chuck
Chuck