Well, after debating to use a switched power line, or always on, I went with always on for now.
It was pretty simple, if you don't want to cut up your deluo cable, get a PS/2 male/female extension cable and hack it up, this is what I did. You need to cut out the 5v supply on the male side, pin 2 (I'm using it though the USB port), and run a wire out of it.
On that wire, you need about 66ohms to keep it at 4.5v @ 130ma (average seems to be 122ma).
The Deluo/EverMore GM-305 can run off of 3.5v to 8v as tested, so even though this is a cheeseball method of getting the right voltage to it, it should be ok.
I took 5 5% tolerance 330ohm resistors in parallel (ORANGE, ORANGE, BROWN, GOLD - 1/4watt each, 330ohm/5= 66), and got around 64ohms from the total. The total max draw is ~1.1w, so you have a 10-20% overhead, but it still gets a little warm. Just put it inline to the wire that is out of the extension cable, and it stays powered.
Good to about 16v input max (7.5v to the unit at this point), and good down to about 12.1 volts from the battery when it is starting to drain. It automatically draws much less current (~20ma) if it can't turn on past ~3.4volts at this point, so in a way, it's a ghetto battery saving mode.
I drew up a schematic that might help you, but test for yourself as to which pin to really mess with (male end, pin 2, going to the GPS). All this information is to be used at your own risk. I'm not liable for you burning out your GPS, or applying voltage to the wrong side of the circuit and blowing your USB hub or PC. Also, I'm not responsible for giving you a jumpstart when you find your battery dead after a week of sitting
To stop the current draw if you leave the car parked for a while, you can simply disconnect the USB from the PC, and that will leave it ungrounded. I suggest a 1amp or smaller fuse on the supply side.
Linear Mode
