What I was contemplating doing was just using something to make a template, then going to a glass shop and having some made up for the sides...I don't think it should cost too much, but I haven't priced it out yet.

btw...the rear window is more expensive than the front from that company you quoted? That just seems odd. But I guess it's a matter of demand, windshields are in more demand so the price can be lowered (because of the quanities made).