A quick search would have brought you to:
Looking For a Car Mount?
And there, I posted the Sprint D710 model is the one you want because it is almost the exact same size as the Skyrocket, just needs to be modified slightly
Universal holders are ridiculous - for the same price, get the one for the phone, you know you can sell it with the phone and make more money as a "package" instead of trying to keep the same ugly car dock that doesn't charge your phone after you sell the Skyrocket! And as for Pro-Clip.... I've been a big fan of theirs for a long time, but the insane pricing and having to hardwire it every time gets really old, really fast.... for HALF the price, you get an OEM Samsung charger that just needs to be modified and then use Bluetooth to get audio to your car's stereo, very simple, classy, and not ghetto rigged like this awful universal mounts!