The cheapest and easiest place for me to order impellers for my Indmar LTR is amazon. $29 shipped. If you can figure out what you need you can check there. I've also ordered them from SkiDim.com but they're a few more bucks and they charge for shipping. If you aren't sure what you need they'd be more helpful than amazon.
It's a black scorpion? This might be you:
"AROUND 2002 UP MERCRUISER
#47-862232A2, Black Scorpion S/N OM391600 and up, S/N OW690000 and up. MX 6.2L S/N OM317000 and up. 5.7 MPI SKI S/N 1A090000 and up. New style pump that has the blue water drain petcock on the side."