Expression for a rare find?

Is there an expression along the lines of

Red cars, for the man, were like the birdwatcher's spatuletail

... assuming the spatuletail is a rare find for birdwatchers. I'm pretty sure I heard something like this not too long ago, but I can't remember what. It was definitely in that format - the profession and then something someone in the profession looks for, is unexpected to come across.

edit: I think I'm starting to recall that the expression was more along the lines of

the archaeologist's El Dorado

..or something similar, where it means a unique breakthrough or meaningful discovery of a field rather than an uncommon but still ordinary find.

Still though, I would like to know if there's an expression similar to the one in the first example.

Answer

I guess you mean 'difficult to locate/find', rather than 'rare'. The commonest idiom for objects difficult to locate is needle in a haystack.

Red cars, for the man, were like needles in a haystack.

This means the man found red cars very difficult to spot.

There are several related idioms for things that are hard to chance upon. A couple of them (also mentioned here):

• scarce as hen's teeth


• black cat in a coal cellar