This is a modified design of Raspberry Pi Stackable Tray (built from scratch though) for Raspberry Pi that features screw attachment rather than default one. The reason is that the default one is fragile and would break easily. Screw diameter is 2.2mm since I couldn't find 2.5mm ones. You can get sources from github and modify the .scad design if you need another diameter. You can also check the OpenSCAD sources at my GitHub repository.