Or you can make your own.
Mix together all ingredients in a sauce pan. Stir constantly and heat until the mixture begins to thicken. Remove from heat and let cool.
Divided the mixture into three bowls. Add a different color of food coloring to each bowl (1-red, 1-blue, 1-yellow). Put approximately three tablespoon of each color into a ziplock bag. Seal the bag and tape the top closed. Knead the baggie to mix colors just enough to look like a rainbow rainbow. Lay bag down on a hard surface and gently press to flatten it. I usually double bag mine.
Shayla practices fingertracing her letters, shapes and words on it.
For more frugal Friday ideas, check out Crystal's.