I've been searching eBay, and numerous Blackberry parts dealers on the web for a black keyboard plate (Call/Menu/Return/End Call buttons) for my 8320 with no luck.
There are no black keyboard trays for the 83XX series. I even emailed Steve over at CNN.CN about it many moons ago, along with an inquiry for black trackball rings.
The best that you can do is to buy a full housing for an 8330 and put it on your 83XX. The keyboard tray from an 8330 will not fit in a 83XX housing due to the different shaped Call/End buttons: