On/off button too sensitive. How do I solve?

I have a Defiant 1500 lumen 4D 3-mode flashlight I picked up at Home Depot for $30 CAD last year. It is fantastic, except the on/off button is way way way too sensitive!! I keep mine in the car for seeing numbers on houses at night (I do food delivery), but it can get accidentally turned on extremely easy! If it rolls around slightly on the floor, passenger seat, trunk, wherever, the button can get turned on, resulting in dead batteries.

It's the light described in this thread:
http://www.candlepowerforums.com/vb/showthread.php?392393-Defiant-1500-lumen-rated-triple-xml2-emitter-4D-behemoth

What can I do to make the switch harder to hit by accident?

1. Glue or bond some kind of stiff "bubble" shield over the button? What can I use for this and where can I get it?

2. Disassemble it somehow to access the underside of the switch (Is this possible?) to somehow add more resistance in the form of a stiffer spring or something, making it harder to press?

3. Glueing/bonding some kind of wall/barricades around the switch so the switch still presses just as easily, but is now inside of a recessed "well", protecting it from leaning into something that will press it?

4. Replacing the switch entirely? (Probably more fuss than I'm willing or capable of doing)

5. Applying some kind of liquid coating or something to the rubber button that once dried, will stiffen and thicken the rubber?

Here's a pic:

If you can get at the switch easily, how about cutting a circle to fit under the cap from material like clear plastic blister packaging? It would add stiffness, but probably not too much

You have a few easy options. Get 2 thick Orings and put one above and one below the button. Like your bumper guard idea. You could fashion a guard of any kind out of a few washers or a nut and JB weld it around the button.

Next, try to Lock out the light by unscrewing it just enough to break the contact? You need to see if this will work on this light. It should.

On lights that have a rear clicky and can be taken apart, I shave the bottom of the button. The part that makes contact with the switch. Making it require more travel room.

I might just go get an automotive hose clamp and put it on, with screw side on same side as button.
I don't have one handy, but they come with option of being rubber lined, that's the one I'd get an use.

Here is a picture of a pipe style screw on clamp..

Hope that gives another option to consider.