White garden rocks are commercially available and can typically be found at a landscaping business in your local area or home improvement store. Check your local yellow pages for these businesses.
You can buy garden rocks of just about any color at practically any garden center or landscape supply store. Even "big box" style discount stores like Wal Mart and Shopko usually carry this sort of thing.
These can be found at most home and garden stores such as Home Depot or Lowes, even Wal Mart. They are a seasonal item usually available in early spring.
