I am looking for this MOSFET but it is discontinued and very hard to find cheap...
what is the next best thing?

 

Simply call Fairchild and ask for the replacement part number.

 

Try these: http://uk.farnell.com/international-rectifier/irlr8721pbf/mosfet-n-d-pak/dp/1551907?Ntt=IRLR8721
They have much higher specs.

Other possibilities, also with higher specs:
IRLR7807, IRLR7821

Compare the total gate charges.

 

wow..thanks guys
might need to brush up on my specs tho..
ill take a look (and learn).

im assuming they will do exactly the same thing.

 

Any of those I suggested have both a higher Vdss and current rating, and the same threshold voltage (logic level).
The only item I don't know about is the total gate charge, normally specified as Qg. If they're similar, or you have overcapacity in your gate driver, or you are using it in a low-speed switching situation, you're good to go.