some of the early metco kits were one piece. You may find one used. but, you'll still need the bracket kit to hold the lower idler in place. Your best bet to save money is to just buy a used metco kit and get the size ring you need.
Since you might possibly swap lowers in the future, the newer ring style just makes a heck of a lot of sense. A whole lot easier to find of course. Give Jared a call at Lethal Performance and he'll take care of you.