Outdoor Camera Mag Mount Hardware Sizes?

I am trying to mount an outdoor camera with the magnetic mount on a thick Hardi board surface (fiber cement material) which should be treated like stucco or concrete.  The instructions to use a 7/64" drill, but that is obviously too small for the anchors provided. I tried a 5/32" drill, which also seems a bit too small, and managed to break one of the supplied plastic anchors.  I should be receiving a couple replacement anchors shortly.

The question is: What are the actual specifications of the screw and plastic anchor provided for the mag mount? Looking at what's available at Home Depot, I could not find an exact replacement. Is this a #4 or #6 size anchor and screw? If so, the recommended mounting hole seems to be 3/16".  Length of the screw appears to be 1".  Simplisafe tech support does not seem to have this information. Can anyone help? It would be nice to be able to source replacements for these parts easily.