Electronic car keys

2008 Chrysler 300. My son's spare electronic key will not work even with a new battery. I even tightened possible loose connections with solder. Anyway, it has been just as easy to use the little manual key that is inside the big key.....until now. The manual key will no longer turn in the unlock direction. It works to lock but not the reverse.

My questions are: what does a new key cost? Where would be the best place to buy one? can I buy a new tumbler? Can i buy one from a junkyard--assuming they keep the keys somewhere?

I know the easy way out is to just buy a new key, but dang, I am getting cheap in my old age. Besides I am saving up for my new Obamacare anti-stimulus package.