There's this cross type one. The heatsink for it is (obviously) right below, and yes, "surprisingly" it is OEM equipment for this system on a card. It does come with thermal paste.
There's also ones that only clip on one axis.
Unfortunately I don't have better pictures of that one. The hooks are just simple rounded metal strips that bend inward slightly. The whole assemblage flexes. You slip the hook under one side, and push down hard on the other, hoping you don't break the ceramic, until it pushes past the ridge of the chip on the other side and gets stuck.
Actually, on this particular design it's quite hard to push in without a screwdriver, and there's no place for a screwdriver to hook, so you'll have a screwdriver at high tension pushing this flexing metal strap down, hoping you don't slip and stab your motherboard to death...