I think you're going to be out of luck on this, might be better off calling a tow.
If it were my car and I wanted to try patching it to get home, I would get a rubber radiator hose. I would cut it so it would be larger than the hole by at least an inch if possible. Then I would slit the hose down one side, and wrap it around the plastic piece with the slit opposite the leak. I would then use several worm gear rad hose clamps to clamp the hose onto the pipe, starting in the middle and working my way to the edge of the rubber piece. The idea is to have the clamps touching each other, supporting the entire metal piece. I would also tighten each clamp until rubber just started pushing through the gear holes on the clamps so as to not collapse the rest of the plastic pipe. On the drive home, I would pay close attention to the temp gauge. If it either spikes or drops, or if I saw any steam at all under the hood, I would immediately stop and call a tow truck. Once I made it home, I would park the car until proper repairs could be made.
If you decide to try this, it's entirely your decision to do so. I still recommend calling a tow truck. The cost of a tow for 20 miles should be less than 100 bucks, but the cost of a new engine can be in the thousands.
