Welcome to the forum Giovanni

there are many AAA lights available. Since you have an Italian name, maybe you are in Europe, so you could search your Amazon, or you could buy from Aliexpress…

this is one of the AAA lights I recommend
https://www.aliexpress.us/item/3256804153636802.html

for your Klarus, if it is becoming unreliable, it might help to clean off all the old lubrication… sometimes it gets dirty and accumulates to block good electrical contact…

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