Plugging in your passthrough via a wall adapter is the way to go (and protects your computer. It is never recommended to plug any type of e-cig charger or passthrough into a computer USB port).
You might have something at home that will work right now. If you have an iPhone or Palm charger at home, that USB plug work just fine (I stole my husbands, ha).
Also a USB hub that plugs into the wall will work great and you will have several plugs for chargers, etc. then. You can these or the iPhone plugs at BestBuy if you don't have any around. Check the fine print / labeling to see if it has at least a 1000 mA (1500 is better) up to around 2000 mA rating (1 to 2Amp).
Also you can to check out your local RadioShack. Just double check that what ever you buy is rated at least 1000mA (1Amp).
Vaping on a passthrough can save battery life when you are in your car.
Car USB adapters for your passthrough can probably be bought locally at Walgreens Drugstores. They are 12v to USB car adapters with 2 USB ports (you can vape on your passthrough and charge up a battery with the other port and a USB 801 charger!) and it's rated for 3amp output. About 12 bucks.
You'll want one of these to be at least 5v and 2amp if possible. The 12v are nice and will run in a Truck (a regular one will not run in a truck by the way... ask me how I know

).
If you are ordering anyway, MadVapes.com has the car adapters. Great prices!
NOTE don't buy the wall adapter from MadVapes as it won't power a passthrough (only a e-cig usb charger).
2 amp Car to USB Adapter
You also can pick up different kinds of USB car adapters at RadioShack
Lenmar USB DC Car Adapter Charger for MP3 : Portable Music Car Charger | RadioShack.com
You can also use your passthrough in your car with a portable battery power pack and also use it while out that day (tucks in a pocket, clip on phone case or purse).
Portable Battery power packs that will work:
Kensington: Good Prophets has one on sale right now! I have several of these and they're great with all my passthroughs.
Kensington Portable Power Pack
or for a little more:
Amazon.com: Kensington Portable Power Pack for Mobile Devices (K38021US): Electronics
Info (and price to buy) on the Mfg.'s website
Portable Power Pack for Mobile Devices - K38021US - Kensington
APC also makes one and it can usually be found on eBay. Again, check the ratings of what ever you buy.
These are also reported to work just fine:
myGearStore Just Mobile Gum Pro USB MP3 iPod GPS PDA External Battery - 4400mAh - Accessories for iPhone, iPad, iPod Touch/nano, Macbook, Blackberry, and more!
Portable Power-High Luminance LED Torch - Meritline.com
Duracell DR7000LI Instant Power Charger for USB Devices at TigerDirect.com
The important thing when purchasing USB wall plugs, car USB adapters and and battery packs is to make sure that they have an output of 5 Volts DC with a 1000 mA (Milli-Amp) output. The mA can go from 1000 - 2500 mA (2500 max range, stay with 1000ish, the Passthrough only draws what is needed for power which is around 1000 mA).
The higher the mAh (Milli-Amp
Hours) rating on the battery pack, the better (gives you an idea of how long it will run before needing to be recharged).
Happy mobile vaping!
