The first one I fabricated used a 1 quart brake fluid can, with a piece of copper tubing soldered into the screw-top lid. Recovery tanks also need an atmospheric vent to account for fluctuating liquid levels, and the standpipe that's connected to the radiator vent tube needs to extend almost to the bottom of the container, submerged in a little bit of liquid so it can siphon coolant back into the radiator as it cools off.
Jerry
