The closest thing, IMO, that I've seen to a loach are northern hogsuckers.
We had a couple 6 inchers in our tank until for some reason our green sunfish took a disliking to them (only fish they've had a problem with) and decided to rip them apart.
They wiggle back and forth and use their mouth to sift through gravel, plus their swimming style and interactions with each other seem pretty loach-like.