My Girl friend's pc has a stock cooler and it's s478
It was getting extreemly noisy, when I opened the case to have a look I found the reason why.
A Layer of dust & fluf had formed between the heatsink and fan, basically it coated the top on the heat sink forming a mat which was blocking the airflow.
I used a cocktail stick to poke between the fanblades and dig out the dust (so I didn't have to take the cooler off the board
)
It's now running quite again.
After much digging I've found the dimentions for the stock intel L 90mm x W 89mm x H 51mm
Not sure how much height clearence you have in that small case, but anything with a foot print of 90x90 should fit.