You can try to rough up the shiny spacebar with some fine grain sandpaper, try p600 or p800 or maybe p1000 grit. Don't go too low on grit, or you'll just make deep scratches. Don't go too high (like p2000), or you might polish that ABS even shinier. Even better would be sand blasting, but unless you own a sandblaster, it would probably be easier and cheaper just to buy a replacement set of keycaps from EK, just for the spacebar.