This is a tough one. Look for oil stains on the fins as any leak will carry oil with it. Maybe you can find a junker to get the upper and lower tubes that go in to it seal them off and connect them with new o rings and find some way to put some refrigerant into it with what is called a tap valve. Do not use air as it is full of moisture. Make sure you do clean the evap out with some flushing agent made for that purpose before installing anyway.
