Right behind the grill there's a small radiator or some kind of cooler that sits in front of the coolant radiator what is that cooler called

 

It should be dimensionally almost the same height and width as the radiator, it's the air conditioner CONDENSER. Some models of G35 it's actually all built together with the radiator (both components soldered together even though the look to be separate) and not separately replaceable.

 

It's this small one behind the bumper it's leaking and it think it's power steering fluid

 

Yep, power steering cooler.

 

Where can I find the direct replacement OEM brand new I can't seem to find it anywhere

 

It's not a wearable item so I would just buy a used one off eBay.

Probably got hit by a rock or some road debris that put a tiny dent/hole in it.

You can also remove yours, hook it up to an air compressor (cap off one end) to find exactly where it's leaking from, then solder the hole closed. You might have to bend the fins over just a little bit to get the torch on it better, just bend them back when you're done.

eBay has some for under $20 though so it's not like it's an expensive part.