Even though my son is more of a 3DS kinda kid, he loves vintage video games and all things Nintendo so he decided this year he wanted to be and oldskool Nintendo Game Boy for Halloween. Here's how I made him one with my sewing machine.
It would have been much easier just to paint the buttons on, but I tend to do things the hard way.
I collected beige, black, gray, red, and tan vinyl and cut out shapes for the buttons, speakers, screen, etc. I carefully ironed on HeatnBond Lite (my favorite thing in the world) to the backs of the shapes and carefully ironed them onto the beige. This helped to hold the shapes in place when I sewed a zig-zag stitch around the edges.
Tip: Never iron vinyl directly. Always put a layer of cotton fabric overtop to prevent the iron from melting the vinyl.