where have you looked so far? there are quite a few good monologue books out there, your school library should have some, as should your local library...other than that look for plays, films, books with characters that interest you and build your performance from there. No matter what you choose you'll have to refine it and adapt it into a coherent performance; there are very few whole pieces that run for as long as six to eight minutes. What kind of character are you interested in playing? i would steer right away from net monologues, frankly most of them are shit, good ones are rare. the only thing you can really do is just to read widely until you find what you're interested in. read a lot of things before you settle on your final choice; looking back i dont think i read enough scripts because i keep seeing pieces i really like but cant do becuase its a bit late to change pieces now after months of work. so yeah dont fall into that "quick quick must find a monologue" trap. good luck!