Make your own. I made a little game about a year ago, and I remember spending hours making little sprites for our characters. It does take a little finesse, but it's worth it knowing you did everything yourself. Download GIMP and play around with it; it's the free version of Photoshop, basically.
By the way, if you are going to produce this game and actually try to submit it, you might run into copyright issues because, after all, you won't have made the sprites, but someone else will have.