As I recall they are an 8-32 with a #6 size head. But a Countersunk head machine screw has a smaller head (0.312") than a Countersunk Socket head screw (0.359"). So you might try some machine screws. Or put up a wanted ad.
Don't quote me on the length. I used 1/2" as a guess to get drawings to show the difference in head sizes.
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I helicoiled mine to 6-32 and used 6-32 Countersunk socket head screws (0.307 head diameter). I don't suggest this because the factory used a Phillips head crew, therefor a machine screw.
