Here is something can be used by many of us. It attachs to the side of the layout http://www.newrailmodels.com/Products/Accessories/Pocket/Universal.htm
Alan: I made my own holder at practically no cost using a solid cover plate from an electrical out and two small pieces of wood to form a "C" clip. I painted it the color of the fascia board, a black finish and it holds my LH 100 handheld device of my Lenz 100 system. It's nothing fancy but it does the job and it's inconspicuous. Stay cool and run steam.....
