a small piece of 'wood' to make a shelf (Fords Farm RG31)

I need an offcut of 'wood' - Veneered/ coated chipboard? (don't know what it is called) to make a shelf for my laptop (I have changed from a tower PC to a laptop and wifi keyboard. I only need a piece about 17.5 ins (44.45cm) x10.5ins (26.67cm) and all I can find online comes MUCH larger pieces! Has anyone got something suitable lying around in the garage or shed that I could repurpose please? Can't recycle the tower unit until I have a shelf! :-) Thanks.