If you can't get raw grassfed butter, I highly recommend Kerrygold Irish butter. It's grassfed, but still pasteurized. It's always at Trader Joe's, I believe Whole Foods has it as well. Sooooooo good...
I know you all read Stephans blog post and thought "Mmmm...butter" instead of "I must eat more fibre so my intestinal flora increase endogenous production of butyric acid" so here's some points to consider before you all get too carried away with the idea that butter is the new superfood -
1: Your body can synthesize all the SFA's it needs so there is no requirement for a dietary source of butyric acid or any other SFA.
2: Any increase in dietary SFA's above 0g/d is associated with a linear rise in low density lipoprotein cholesterol levels and consequently an increased risk of cardiovascular disease.
3: Butter contains only 5–6% butyric acid so you'd need to eat it in fairly large quantities if you wanted to rely on it as a significant source of butyric acid.
"Eat food. Not too much. Mostly plants." - Michael Pollan.
This would come as a surprise to many people around the globe who have valued butter for its life-sustaining properties for millennia. When Dr. Weston Price studied native diets in the 1930's he found that butter was a staple in the diets of many supremely healthy peoples.