What's the cheapest way out?

My neighbors kid was helping me wash the 500sel benz I had just bought earlier and I had to disipline him for a number of things not harshly , rather nicely, well any way I wanted to start the car and my keys were no where to be found well after 3 to 4 hrs later he tells his dad he took them but can't remember where they are, my dilema is the only money I had left was to smog insure and register the car. where can I get a new car key made and does any body out there know a real cheap locksmith? I called a few but because it is a mercedes they say I'll probably need to go to a dealer which will cost $400.00 leaving me to have to resell the car for alot less than what I payed please someone have a solution for me THANK YOU>