Best Place to find a real one, eBay.
Cheap as Heck, and, well, that's about it.
DIY Techniques?
The Pen Trick WORKS.
You need a HARD-PLASTIC pen, like a CLEAR Bic Pen.
NOT one of the soft white/black/whatever ones.
You remove the ink, the metal tip, etc, so you're only left with the hard plastic barrel.
Grab a lighter, heat up the tip. Won't take long, just get it nice and soft, it may start sagging a bit.
While it's still good 'n' hot, JAM IT IN, stick it right into the screwhole, down onto the screw, give it a firm push, and WAIT.
It only takes a few seconds. Count to 10 or something.
NOW twist, while pushing down, if you didn't *Can'tSayThisOnTV* up, the screw will come out with relative ease, may as well be using a screwdriver.
If you did things right, and DIDN'T LIGHT THE Dang PEN ON FIRE (Some people say to, ignore these people), then your pen is still useable too!
You can easily get out more screws, Heck, you should be able to get at LEAST a half-dozen before it's too worn out.
Then? Just heat it up again, repeat.
PRO-TIP!
Yes, with relative ease, you can make your own tool for this purpose, all metal, high quality, last you a life-time, etc.
You need a tool to start with, and I've seen a lot of people use Flathead screwdrivers.
It's what I used, works fine.
Brunoip made one from a hexagonal piece of metal, as seen above. Dang impressive if you ask me, and an awesome idea.
No matter what, the technique is similar, and relatively easy.
Grab yourself a good file and get going!
With a flathead screwdriver, you'll be filing out the center of the tip, so you're left with two prongs that fit over the head of your screw.
Works like a charm.
As for the more advanced (and more than likely far superior) method, using a hexagonal piece of metal like brunoip...
Well, it's pretty much the same, look at his picture, it'll tell you really everything you need to know!