According to the Squadron/Signal Messerschmitt Bf 109 In Action, Part 2, the Bf 109 late G-5 through the K-4 had the same back armor and armored glass arrangement. There was no headrest. There are very clear drawings of this on pages 39 and 48.
I'm sorry that I cannot post these pictures, I do not have a scanner. You should be able to get this publication in any good hobby shop. If you cannot find it in your area
, certainly Squadron Mail Order has it.
Pete