Hurshel,
I made a clamp out of a marine Starboard material that goes around the bar. I always travel with the door open also, after rebuilding my shower.
I had a strap sewn that is a proper length to go around one of the rollers and maintain a little tension on the roller when snapped. This was my second idea at a method of latching the door open. In thousands of miles of travel now the strap has never come off so I consider it well tested and safe. The strap end has a male snap fitting that screws into the aluminum shower frame. I used a right angle drill to do that. The other end of the strap has a female snap on it. These are standard stainless marine canvas snap fittings. After the strap was installed I find that the clamp is redundant and not really needed. I push on the door while in the open position, work the strap over the roller which has a recess, then release the door and there is now tension on the strap. I do not unsnap the fitting at all. Very simple arrangement....
My strap is made out of sewn Sunbrella material and the only install issue is to drill the snap fitting hole in the right position on the aluminum frame to allow for some tension on the strap when it is wrapped around the roller. With the door riding in this open position there are no longer any wear points in the used portion of the plastic roller runner, that is installed on the top of the shower bar/frame, like there was with the door riding in the closed position. Well worth the effort for this change.
I also spoke with Newell and was going to order their acrylic "clothspin" for lack of a better term. It worked by pinching the two glass panels together and I was not sure of that arrangement. Gerald has tested that now, I would certainly trust his judgment, so there are several options to secure the door in the open position. Parking the door in the open position, supported by the existing glass panel and frame, is certainly a far better option for this assembly then riding on the unsupported bar.
Later Ed