Bob,
Your laptop probably does not have a serial interface, but, if it did....
You could probably pick up a hand held garmin - an older one, for next to nothing. Not that ive done it, but they (at least some of them) have serial interfaces for connecting to a computer.
You would have a bit of a bonus then of having the hand held unit too, which sometimes comes in useful.
I dont know how much usb gps units cost, or what you want to do with it - or what software you want to runm but its a consideration?