Sceince fair project would like to build a remote locator (keyfinder)

I am just getting back into the electronic field after 15yrs out of college. (So I just have a general concept for now.) My 10 year old son and I would like to build a circuit to locate a lost remote for his project. We have looked at a few key finders but they were clappers basically. We don't want to reinvent the wheel so if any body has any old diagrams or ideas please feel free to share. Thanks in advance!!

This may give you something to go off of.

It is a beeper finder. Basically it beeps on the FM band. Connect it to the remote and you can find it using a FM radio to follow the beeps.

Build a little FM receiver tuned to the same frequency if you want to use LED blinks opposed to noise beeps..or both

Thanks looking into it now

TALKING ELECTRONICS LED Torch

Here is the page I was looking at.