The IZH uses this thread size in several places. The grips screws are 15 mm long, and the “pump lever handle” (#47) screw (#48) is 10 mm long. The palm rest screws (#79) are longer, at 20 mm. Because the team I help coach has about 20 IZH's, I bought a box of 20 mm long screws & cut them down if I need a shorter one.
Metric Cheese Head Slotted Machine Screw, Zinc-plated Steel, M4 Size, 20mm Length, .7mm Pitch
The head of the McMaster Carr cheese head screws are still slightly oversized for the IZH, but they are close enough that it doesn't take much filing to get them to fit OK. They aren't available in black, but Brownell's Oxpho Blue does a nice job of blacking the heads & ends of the plain steel ones.