Anyone ever thought of attaching one of those real folding handles to the outside of the part of the doorframe that folds in/out? Folded out when the TM is set up, the handle could stick straight out by having it "folded" at 90 degrees, parallel to the doorframe, and when the TM is folded down, that handle can sit in the space in front of the lower half of the door, perpendicular to the frame. You could put bolts all the way through with a backing plate for strength.
Something like this:
http://www.campingworld.com/shopping...and-rails/5154