I just stumbled upon a website, Cellular Nationwide Network, that sells aftermarket BlackBerry parts. This means that you can pick up an extra battery cover, keyboard, and even screen for your BlackBerry for relatively cheap. They sell parts for every BlackBerry model from the 7100 to the 8300. It used to be that if you wanted spare BlackBerry OEM parts you had to buy a broken device from eBay. Personally I know one of my friends bought a black cover and sideplates from them for his Verizon 8830 so that he could replace the silver casing with a black one.
They sell practically every part of the casing for many models of BlackBerry’s so you can replace broken parts. Notably missing from the selection is a replacement LCD screen but I am not sure if that is even user replaceable. Keep in mind that for every one of these parts you will need a Torx T-6 screwdriver to open the case of your BlackBerry. They do sell two models of Torx T-6 screwdrivers for $3.00 and $4.50 for the higher end model. Also as a disclaimer there are no guides provided by Cellular Nationwide Network on how to open and replace these parts so BE CAREFUL!!!