You could just carry it in your pack with the batteries removed (but nearby). Or alternatively, open the flashlight and slip a small piece of cardboard between the positive battery terminal and the electrical contact inside the flashlight. The cardboard acts as an insulator. You can remove it when you need the light to work.

Either of these options requires you to open the light - before you can operate it. But both are the surest ways to avoid draining your batteries, if you are hiking for long times during the day (and the flashlight is in your pack).

cheers,
the other Pete

I'm using a piece of electrical tape over the last battery terminal for that. It's better insulator, doesn't absorb moisture, stays in place better, and you can stick it to the side of the cell when not in use so it's harder to lose.

The battery lasts over 50 hours, so like I say it hardly matters if it is left on for a few hours before I notice. I'll always notice just before going to bed at night. It runs on Eneloop AAs, which I stockpile, so it's no trouble to swap in a new one and recharge the old, and virtually no financial cost.

It has a two-stage piston switch, so if it were an issue I could unscrew the barrel by half-a-turn. Then it becomes a momentary-on switch, which is much less likely to stay on for any length of time. I'd rather do that than anything which would involve disassembling and reassembling the torch in the dark. I don't bother even with momentary-on, because it happens so rarely (only a couple of times in the 9 months I've owned it) and because it doesn't much matter when it does happen.

I live and work in an urban environment so I don't want to leave my torch in my pack, even during daylight. During my recent holiday I had to deal with unlit lavatories that were dark during daytime (and had no paper, but that's another discussion). The D10 is a single AA torch that's small enough to always have on you.

I just found out that they make glow in the dark covers for the clicky switches...

A belt holster is the best option. But when I pocket carried a D10 I unscrewed it enough for momentary.

After a month of pocket carry, it turns out that isn't a problem. The switch is firm enough that it hasn't turned on by itself.