Bicycle Mechanics - Just crashed and destroyed my rear derailleur hanger. How do I go about replacing it?

Hey. I always try to avoid dealing with bike shops and the like. I'm getting to be pretty handy, but I've never had to try and replace a derailleur hanger before. And I don't know how to be sure that what I order online will fit when it gets here.

The bike is a Argon 18 Cobalt from 2009. If that can be of any help.

I've found something which looks similar on JensonUSA.com but there are no markings on the broken part, and I can't see the replacement from enough vantage points to make sure it would fit.

I need help.

Edit: Thanks Dan! that Wheels Manufacturing link enabled to find what I'm looking for in about 10 seconds! Hanger 49 seems to be a match. Awesome.

Wheels Manufacturing has the most complete line of replacement hangers I'm aware of.
http://wheelsmfg.com/content/view/686/27/
There is also a page where you can search by manufacturer, but since many manufacturers use different hangers on different models, the best plan is to carefully match up your hanger to the pictures. That is difficult to do with a mangled hanger, but pay particular attention to the location and number of mounting holes, the shape of the relief portion and the overall shape.
I've matched up numerous hangers in this way, and never had a miss match.
Once you find a match, you'll have to find someone to buy it through, as I don't believe Wheels sells direct to the public.

This might be helpful too. sorry about the picture quality. I usually don't dabble in posting image online.

http://img651.imageshack.us/img651/7500/dsc01698vo.jpg
By plimogz42 (http://profile.imageshack.us/user/plimogz42) at 2011-07-17

http://img695.imageshack.us/img695/3532/dsc01696p.jpg
By plimogz42 (http://profile.imageshack.us/user/plimogz42) at 2011-07-17

I'm looking at this as a replacement, but I'll go see what Wheels Manufacturing has on offer as well.

http://img835.imageshack.us/img835/4562/rd265z03trekfisher.jpg (http://imageshack.us/photo/my-images/835/rd265z03trekfisher.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

There are several dealers that sell a range of replacement derailleur hangers. Here's one:

http://derailleurhanger.com/?ppcseid=2094&ppcsekeyword=derailleur+hanger&mmtctg=68252477&mmtcmp=2480597&mmtmt=2&mmtgglcnt=0&gclid=COuMuPeriaoCFSI55QodwG9K0A

Another method is to go to your bike manufacturer's web site and see if they sell replacement hangers for their bikes.

http://derailleurhanger.com/argon.htm