I've had one of these Laserlytes as they're called for at least a year or a year and a half. I keep it nearby some electronic equipment that is poorly lighted in order to give me a better view of some meters. It's worked out well for that purpose in that it doesn't contain a momentary switch. It's switch is a slide switch that's either on or off. Using the equipment requires frequent views of the meters, and the little light staying on comes in handy. By the same token, the switch comes on accidentally far to easily for pocket carry or keychain use.
I was trying to remember where I got it, and it seems like it was Fry's Electronics. I haven't yet needed to replace batteries, but it opens by four screws holding the halves together. I'd suspect the switch manipulates one lead of the LED, and battery replacement is simple, but mildly frustrating holding the switch and LED lead in place while rejoining the halves.
