What's it do? Or what I mean is, to turn on power to the hub when the PC is on?
What kind of USB hub?
Does it switch 5V, or 12V unregulated to a supply going to the hub?
What is the maximum current it needs to switch?
Can you use 12V from the PC to control the relay or only 5V?
How much lighter do you want?
How much are you willing to spend?