One thing to note is that if you can't find gears just exactly the right size, you could raise that center gear a bit to adjust the spacing.
That could be a real finger-removal operation, too. I remember Sheldon Brown commenting how one of the hazards of fixed-gear bikes was that they were more dangerous to work on as the chain, sprockets, wheel and crank all spun together with a lot of momentum, and one finger in the wrong place and it was gone.
Don't remind me. I have had my finger under the chain half way around the chainring on one of my track bikes. This happens when you have the bike in a repair stand and are spinning the crank with one finger, it simply slides up the crank arm and under the chainring, lacerating the finger tip, filling the wound with grease, and then you have to turn the crank to get your finger out.