These are the famous GUI interface that made Bill Gates's fortune. If you already have a good symbol in your logo, all you need do is simplify the logo. You'll probably want to use the same colours and basic shapes in any case. Otherwise it's really quite easy to make your own simple trademark symbol from scratch. If you really must, you can take the easy way out and get a free icon design.
Thousands are available, so there's sure to be something appropriate.
Just don't go overboard in building up an association with your product. There's no guarantee you won't be sharing it with several others. If you want to have a shot at creating your own icon, try this. Type a list of keywords that describe your business. Switch to a symbol typeface like Webdings.