Are internal fans for laptops standardized at all?

[Maetryx]

My son's ASUS K52 series laptop is overheating and he suspects the cooling fan. He's probably right, from the description. So I tried to look up how to buy a laptop fan. Holy smokes! Are no two laptop fan (or fan assemblies) alike????

Where can I buy one or how do I know if there are compatible fans out there?

This image is from a similar laptop.