There doesn't seem to be any way to "find" anyone unless you already know them from somewhere else. How do you make new acquaintances with similar interests? What's the point in marketing via Twitter if you can't figure out how to get heard?"
This is a real concern, but thankfully there's several resources that can help you expand your network of friends on Twitter.
Another great way to find people that share your interests is with the Twitter Packs wiki. Here you can find Twitter users by subject matter, you can find companies that have a presence on Twitter, and even locate people by region. If you are interested in meeting other Twitter members that focus on 'jewelry'. for example, you can view the list, and even add yourself to this same list so that other members can find you!
My favorite search tool for Twitter is Tweetscan. With Tweetscan, you can search for topics, people, places, anything. You can also search and make sure that you have seen all the replies to you that other Twitter members have left. Just search for '@YourTwitterName'. Sometimes the web version of Twitter as well as Twhirl will miss some of your replies.
But perhaps the best way to meet new people on Twitter is to follow the people that your friends are following. Watch the conversations unfolding, and if you see that one of your friends is having an interesting conversation and replying to someone that you aren't following, then click on that person's name and check out their Twitter page. It could be that they are someone that you would like to follow.
With these tools, you should be able to expand your Twitter network significantly. And the best part is, your Twitter experience becomes much richer and more rewarding as you follow more people.