"This is the second temporary window I put in my ex-wife's car. The first was made from plexiglass and hotglued. It lasted almost 2 weeks... It was getting ready to...
Duct Tape
"Classic duct tape and trash bag repair but on a larger scale."
"I spied this car and managed to get a pic of the hood that was duct taped and bungee corded down. At least the tape matched the paint."
"I got bored one day and had some duct tape sitting around and this is what I came up with to fill some time."
"Just yer average WT duct-tape-and-plastic car window..."
If you can afford the BMW then you should be able to afford to fix it. Points noted for fancy duct tape.