If you use it in your car you might be able to use the charger there.

There are also miniPCI (Express), ExpressCard, PCMCIA, and USB WiFi/GPS/3G solutions so it is possible to build your own. A portable laptop with good battery and such a card with a converter for the car charger might cut the bread as well.

While 200 USD is a nice price, be careful it isn't SIM locked. You might want to take out the SIM and put this in another device such as a USB 3G stick for your laptop to take with you, or your N900.

All this besides the obvious alternative, (smart)phone.