Cathy,
What are you going to do with it? Use it to top pots of seedlings or to mix in with potting soil as an aerator/drainage amendment? If the former, a bag of "Play Sand" should do the trick. If you plan on mixing it in with your potting soil then go with builder's sand or old aquarium grave - which can be quite large, but it works. Builder's Sand is generally a coarse grade of sand while play sand is a lot finer. Lowe's, Builder's Supply should carry both.
Rebecca
Nature is trying very hard to make us succeed, but nature does not depend on us. We are not the only experiment.
- R. Buckminster Fuller