Certain online retailers will carry any computer part you could possibly need. Whether it be ibm laptop batteries or a usb to rs232 converter, the internet has got you covered. Some items should probably be considered before purchasing others. It does not make much sense to buy usb converter if you do not even have any usb ports. That would probably never happen though, since every computer made in the past ten years is sure to have one.
A better example would be a laptop battery charger; you wouldn’t buy a charger if you didn’t have a battery, would you? Of course not, that would be silly. Unless your computer runs directly off of the ac charger. It really isn’t such a silly idea in retrospect, since you would still be able to use your computer.
Who doesn’t have a battery for their own laptop though? Having a laptop without a laptop battery is like owning a telescope when you don’t even have eyes. That was just a joke. Batteries need to be replaced all the time. They can break, they can go missing or pesky coworkers trying to play a prank can steal them. If people didn’t need additional batteries for their computers, they probably wouldn’t be sold online. If you wanted to be super prepared, you can always preemptively buy multiple batteries. This way, if your coworkers take your battery the joke will be on them and they will be left to face their own sense of guilt when they realize they took your battery and accomplished nothing.