Unfurl an age old plot to destroy the university using a basilisk, freeing a house elf in the process. Clothe the house elf and befriend it. Ask it to take you into the university at the risk of its own life. Mourn its death after it is stabbed. Bury it and mark its grave with a large rock...
You might want to invest in a broomstick as an alternative. Random Chinese stores have them for like 2 or 3 dollars. Go for the plastic ones; the wooden ones start to rot in rainy weather.