You should be able to repair your existing door.
Have a look around the perimeter of the door to see if there are any screws, particularly near the handle. You are looking to take the front fascia off the door, so that you can access the inside. Most doors have the front fascia held on by small brackets glued to the back of the glass that clip on to a fixing on the internal door. The top of the fascia is normally held in place by the handle.
Once you have the front of the door off you can retrieve the piece of glass that has fallen out. You will almost certainly find that the glass has come away from the adhesive that was used to hold it in place.
You will need to clean up the glass and the metal door and re-stick the glass using a high temperature oven door glue