You probably can. If you still have the manual, check there to see what kind of battery it says you need. Otherwise, open it up and take the battery in to wallmart and ask them to find you the same one.
If you have a radio shack near you, they will have it most likely if wallmart doesn't. That's where I got mine.
I thought of you this morning when I had the exact same temp as yesterday!
Good luck, hope you find it!