ON makes Caesin protein which is absorbed "slower" then whey etc. I'm sure there are other companies as well. I hope thats what you are asking. Hope it helps dude.
Also, milk protein is a good source of casein(something like 80% casein, 20% whey). So foods like milk, cottage cheese, and yogurt are good sources, as well as milk protein isolates(which seem to be cheaper than pure casein). Check out True Protein, they have a lot of options when it comes to protein and you can do custom mixes as well.
the best is whey isolate with all natural peanut butter, itll slow down the digestion of it