Well...it looks like either a brick to the window ($500)...or a "wait-out" for ordering a new key (which you should have done originally which would have totally prevented this frustrating situation....and yes...I'm kicking you while you're down..but only as a kick-in-the-butt to others that are in the same situation as you and are procrastinating a spare key purchase)
I really empathize with you...but living without a spare key is not worth the frustration you (and many before you) have to go through when your only key accidentally gets locked inside the vehicle. There are multiple key types...so the more expensive remote key doesn't have to be your spare key of choice...there is the much less expensive plastic spare key that could be sitting/waiting patiently in a drawer...awaiting to be used in a situation just as you find yourself.
Good luck with whichever decision you have to decide.
Key #3 & #5 in the diagram below are what's available for the e53. The set (#16) costs about the same amount of money a new window will cost you (approx $440). And key #3 cost approx $44 (USD)...which is way cheaper than replacing a window.
