AC for Vertical Sliding Window

  Its getting pretty friggin hot here, and its making it hard to get motivated to do things and get a decent night sleep.  I would like to put an air conditioner in my window, but my window slides open and closed from left to right, instead of up and down.  Now, you can get a new airconditioner for a a regular window for around 80$, but the cheapest I have seen for my sliding window is 250!  Does anyone know a good way to rig a conventional a/c to fit in my window, or know where to get a cheap a/c for a sliding window?