You've probably developed a solution by now -- 3.5 months -- but I'd like to put in a second opinion that most people might not think of -- industrial strength velcro! They sell small (15') spools of the stuff at Home Depot, and we use it extensively for electronica around the house. I even have a TomTom GPS w/ 5" screen hanging from a velcro strap in my car, rather than a dash mount. It's easy to pull off if you're entering addresses, and it just slaps back in place.
For the TK45 (I just ordered one today), I'm putting one mounting velcro strap in the same place under the thwart in each of our 4 canoes. I'm putting one mount on the back of the front passenger seat in the car -- easy to just reach over and grab it. (Be careful when you choose mounting locations where your Fenix might get launched forward in a collision; I don't think velcro alone would be good for that unless you have solid backing like this seat. That means avoid the overhead and the car doors.)
And if you don't mind the tres-geek look, you can put velcro on your camping vest to carry the Fenix, a compass, Ipod/Zune, etc.
This industrial-strength velcro isn't the same light-duty stuff we grew up with. The only thing you want to be careful of, the adhesive backing glue tends to re-liquify above 130 degrees or so. it's not good holding an EZ-Pass badge to your front windshield. But everything else, it has worked out very well so far ... and those carrying holsters tend to cause as many problems as they fix.