Stores that sell a microscope?

i dont need a high tech one, just a cheap one that will be able to see bacteria in water... do you know any stores that would sell a microscope thats not expensive, cause im pretty sure im only going to use it once for this science fair, and i dont want to ask the teacher to use one of his because then he will know i only started my science fair now, after ive had 6 months to start it... so any stores that sell microscopes?? thanks