Folding Keyboard
Unless you have a massive laptop you're working with a limited keyboard (and even then there are no guarantees). Carrying around a full sized keyboard isn't exactly practical, but don't give up on having that number pad just yet. The Folding keyboard rolls up and easily fits inside a laptop backpack or suitcase. It's waterproof, dustproof (read crumb proof) so even the craziest all night LAN parties won't bring your portable keyboard harm.
$25
I worked for this company. The keyboard does not work well, and it will break after about a month. It is not a good investment.
It’s pictured here with a mac but according to Barnes and Noble the keyboard is only compatible with PCs