For my Dodge RAM CarPC install, I used an IOGear 7 port hub. The external brick supplies 5 VDC out. I cut the brick off and powered the cord from the 5 VDC output from my Carnetix PSU.
I am doing a CarPC install in my new car (1999 Toyota Avalon) with the hub in the trunk and today, I am ordering the same hub.
IOGear and others make smaller, cheaper hubs but I chose this one because it had plenty of ports (7) and could be directly powered by my CarPC PSU.