The spray you are looking for is called "blossom set" and is available at some nurseries, but you can also order it on line or through a catalog from a lot of places, such as Gurney's, Totally Tomatoes, or Burpee. It is sprayed on the tomato blossoms and helps them to mature into tomatoes.
If it is for food like tomatoes then you may want to try looking at your local nursery for it. If they don't have it then they may be able to tell you where you may be able to get it. Maybe even Home Depot or Lowe's too.