Oh man, I hate those noises. Even if it's on the wifes bike while riding next to her....
I looked for one in the area of the crank arms for a month once, until I happened to lean on the seat just right and got that same click.....
The wife and I both listened to one on the wife's bike for weeks, left me chasing everything under the sun, until realizing the dam kick stand spring wasn't strong enough to hold it up through the bumps....
Just about cried when I found that one!
The easiest way to try and isolate the noise is to start with the frequency it happens at. Like tire speed or crank speed for instance. Then there's noise under power only, noise while pedaling only, etc. In other words, try to isolate as best possible. That effort will generally pay off.
Loose spokes, loose pedals and crank arms are common places, and many don't know the seat post and clamp should be lubed with a light layer of gease.
Another I found, through a tip here, was the grease seals on the front axle. If they're dry, they'll generate a squeek as well. -Al