Donna, I needed one for school myself recently and found one at Walmart for about $8. They had a range of scientific calculators--I think as low as $4 and up to $25. I opted for a very basic one with a moderate protective cover, since it's just going to be on my desk and not traveling to school and back.
So I'd check out your local Target, Meijer, Walmart, etc. You can probably find plenty at Staples, Office Max, and online, but I bet you'll pay more for the same basic item.