What he is talking about is probably not related to the 3pt hitch at all. Think of receiver and hitch on your truck, then imagine a similar receiver type opening under the tractor rear axle. This is where the referenced DRAWBAR is inserted, and the drawbar he is describing as needing is inserted at that point. It is pinned into the receiver just as a trailer hitch is pinned into the receiver on your truck.
This is at least what I gather from all the posts. I have two tractors, use both with a multitude of implements, and have never removed either drawbar from its location. I have chain hooks (from TSC) on both and I use them for pulling logs or towing. With a trailer ball, they would also work well for pulling a trailer if they were long enough to slide out closer to the outer edge of rear tires. Mine are drilled with multiple holes to allow variable lengths to accommodate multiple tasks, so they are easily slid (inward) out of the way, but always available on the tractor.
I would think the best sources are a tractor dealer or a machine shop. I am sure neither will be cheap.