21 year old girl looking for accommodation/roommate in central Paris

I'm a 21 year old belgian-american girl looking for an apartment in central Paris, preferably near the 7th, 6th, or 5th arrondissements (close to the Sorbonne, where I will be studying). I like to have fun and go out, but I also appreciate time alone and am very studious. I am also very clean! I am looking for someone relatively my age who is also searching for a flatmate for the semester (september-december). I am currently searching for accomodation, and would love to find a place where I would not have to live alone, as I do not know anyone in Paris yet.