depending on your phone, you can use it as a modem tethered via usb cable to your laptop (or bluetooth, etc), and use that instead of a laptop card.
You'd need to add Verizon's data plan to your phone along with the tethering option (they'll know what this is).
actually, for just a day of use, I think you can just DO it, and they'll charge you per kb. Its expensive, but if you don't want to add/cancel for a day of unlimited use, that's probably your only option.
What's the big deal about adding it and dropping it a day later? They usualyl pro-rate the charge per day.