I got a purple one from Rite Aid for $9.99 You really shouldn't have too much trouble finding one if you have a pharmacy chain, Target, Walmart, etc anywhere near you.
I know it seems like a lot at first, but I tell you, once you get the hang of it, it's really easy and you're so happy that you do it, because it gives you LOADS of information.
Welcome to the Wonderful World of Charting!!!