Most of the originals seem to be 8-32, but the aftermarket ones are 10-32.
They are pennies each, so you can buy both if you don't have a pawl with you.
Also, they come in Cup Tip and Cone Tip, so be ready for Hardware Store Guy questions.
Finally, you can use a Cap Head Screw rather than a Set Screw
Directions on switching the crappy EBD Linear flippers over to snappier standards here:
https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers/page/11