Ummm, you could ask nicely if they'll let you download MS Office Professional, which should have it. I doubt they'll take kindly to it though, it is not a free addon by any means.
Or you could have a look at Openoffice, which is a replacement for MS Office that has an application called "Impress" which is a powerpoint like application that can output Powerpoint presentations if you change settings when you save the file.
Openoffice:
http://www.openoffice.org/