So this eveing I was pulling off my back cover and the tiny plastic piece on the botton the cover that the latch holds on to broke off. does any one know where I can purchase just a new back cover?

same thing happened to mine, i just bought a clear plastic hard case from ebay for like $6. been a lifesaver from all the times i have carelessly dropped my phone. the case is somewhat disposable after 6 - 8 months though, but for what i paid for it, and the fact that it doesn't matter my back plate is broke, its worth it

If you go to RIM's online store, you can order replacement battery covers for the various model phones, although I believe that the replacement cover for the Pearl will only be available later in November.

go to Cellular Accessories - 3G, LG, Samsung, Nokia, Mobiado, BenQ-Siemens, SonyEricsson, NEC, Sony, Motorola they have many parts for good prices

This site has a lot of replacement parts. This might be what you are looking for
bb-8100-05 BlackBerry 8100 Pearl OEM dark grey battery cover - Cingular bra- Tools, HTC, BlackBerry, Accessories Store, Acer, Alcatel, Mobiado, Nokia, Panaso