Steampunk is more than a "look" -- it's a growing subculture that may have started in the 1980s and the word itself may have been coined by the science fiction writer K.W. Jeter. It usually revolves around sci-fi, fantasy, and the Victorian era after the advent of steam power, but with many present-day high-tech devices either modded to simply look Victorian-made or built entirely from scratch.
If your seamstress and tailoring abilities fall short, there is a large number of talented seamstresses and some who also do tailoring right here on dA as well as many artists who make custom props and jewelry. Most of them do work on commission, but you can also look for ready-to-wear garments and props at such places like amazon.com, JCrew, and second-hand stores if you want to put together the look yourself. Steampunk will probably be filtering into the mainstream more and more, so if Steampunk's your thing, then