I saw the episode years ago. I think one of these is what you're looking for:



I don't know just what exact product Richard used, but these works the same way. Install under the sink furthest from the water heater, plumb into the existing hot & cold water lines. The pump also needs power; if there is an outlet above the vanity, you may be able to fish a wire through the wall from that outlet into a new outlet in the vanity cabinet.

When you push the button, the pump is activated and it draws cooled-off water from the hot line and backfeeds it into the cold line until the hot water reaches the pump, at which time it turns off.

(P.S. -- You may notice some similar but less expensive options. Those other options are the pumps only; they don't include the plumbing kit which you'll need in order to hook it up.)