Replacement Curb Idle Screw AVS2 Carb

If I recall correctly, it's just a #10-32x1 1/4 or 1 1/2 machine screw (double check that first)- should be at almost any hardware store. While you're there get a small diameter compression spring to fit it; you may have to trim it to the correct length. Unless yours is still serviceable.
I've done it a number of times with incomplete/parts carbs.