I may have mentioned it before but I purchased several Olight i3 single AAA lights for my boys. The lights are very small in diameter, weight about half an ounce and have a pocket clip. If you clip them to a pocket next to a knife you are likely to forget it's there. I don't remember if they are regulated but a quick visit to their website shows the output at 70 lumens for almost 45 minutes, 20 lumens for 90 minutes & 2.5 lumens for 20 hours. We've had no problems with them and they were just over $20 each.

No affiliation; just a happy customer.
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"There is not a man of us who does not at times need a helping hand to be stretched out to him, and then shame upon him who will not stretch out the helping hand to his brother." -Theodore Roosevelt