[jano11]

Make it out of very thin plastic card, cut out the areas with the holes.
Make it again out of thicker plastic card and cut the areas with the holes a wee bit smaller.
Glue the thiner one on top of the thicker one.
Find the right square mesh for the cut out areas, cut it to the right size to fill the areas in the thiner one and glue them on top of the thicker one.
Fill the gaps between the mesh and plastic card with putty, sand it and prime it.

This is how I would do it, If I wouldn't go the easier route of making a 3D model of it and ask a 3D printing service to make it for me.

Hope it helps.