Is there a good key finder I can buy?

I’m looking for something I can attatch to my dad’s keys or keychain that he can use to find his keys when he loses them. He loses them at least 2 times a week i swear! something that can be found in distance, something maybe like a beeper conencted to it when you call it maybe? I don’t know, does any one know of any specific gadgets??

thank you!