Air tag advice

[growon]

I'm looking to attach something physically to my sons iPhone maybe under his case, would an air tag fit?

He has lost his phone a few times now and find my iPhon is rubbish. He's going abroad soon and I won't be able to go looking for it!

How will that help? If he's lost his phone he won't be able to locate the tag. If he's lost his phone, you won't be able to call him to tell him where it is.
either you need a lanyard or something or he takes a cheap phone or he loses it and has to cope without and learns a harsh lesson.

Does the air tag not just work on find my anyway?