is this the windscreen you want replacing?
if so you must not use plastic/perspex etc as a windscreen, far too dangerous and i'm pretty sure it's ilegal for that very reason..
can you imagine the carnage if you had a bird strike, not to mention the window "coming in" at 100+mph!!!

**edit**
Just read it again, pretty sure you mean a side window if so just ignore all of the above!

steve