I have a Canon Powershot G3. It has an internal two-stop neutral density filter that you can select from one of the configuration menus. I mostly use it when I'm trying to do fill-flash work in bright sunlight, but it sounds like exactly what you need. Of course, keep in mind that non-SLR digital camera tend not to let you stop down to f/22 or even f/16. As others here have said, you may need an external neutral density filter as well, depending on how long you want to drag out the exposure.