I am a huge FAN of Velcro thin white strips when I do things on the outside of the TM. I HATE drilling into the sides it makes me nervous. Clean the area that you want to place something and it will stay. A little caulk on top would work just fine. The best place to buy white Velcro is your nearest sewing/quilting shop in your area they have so many other neat things.
I had a plastic piece break off on the side of my TM and I did the Velcro and it will be there for ever, it is just like duck tape and vice grips
I carry it with me all the time I gave up on glue and drilling.
Dave