Just make a smoothy out of it, and you won't have to add any protein powder.
Ribeye is tasty because it has a lot of fat in it. Why not just buy the highest fat content pre-ground hamburger at the market? Or buy ground sirloin and tell the butcher to run it through again with some extra fat cuttings.
Or, just buy the ribeye at the butcher and ask him to grind it for you. But duck quickly because he will most likely throw a knife at you.