Ace Hardware is where I bought the 1/4-20 bolts, on the assumption they were correct! I didn't see any 12-20, although admittedly I didn't look - but I don't recall seeing that as an option when I searched the aisle. You can't buy them on Amazon (I've looked), and a general search doesn't provide a supplier. That may just mean I haven't searched in the right place, but I'm striking out so far.