Depending on your dogs, there are a few things I've seen that might work. I currently have one of these in my house, for the door from the house out to the garage:
http://www.secretscreen.com/index.html
We got the striped one, and our dog will stop at it if it's down, as if it were a real door, and wait for us to open it to let him through. I am thinking it could be mounted on the outside of the TM just over the door, perhaps, and you could use it that way.
I don't have my door side available currently to look at the clearance, and it will obviously matter if you have an awning or not. Other options could include hanging screens, but those all open at the bottom and I'd think that most dogs would just walk through those.
On a different tack, it may be possible to engineer a half-door to attach to the cabinet that is right next to the doorway, or event the inside wall on the door hinge side, and then fashion some kind of extension for the upper part that attaches when the TM is set up, but I've never seen anything like that.