Pretty sure you don't need a special recirc water heater, you just add a small circulating pump to the return line you have to add right by the heater, and tee it into the intake, check valves added accordingly obviously. For even more control a small temp sensor at the end of the run that can cycle the pump, or you could just put it on a timer if you don't want to run it all the time, just recirculate when you are likely to be using hot water which will save money. You don't want to use a tankless if you're circulating, they are better served with home run piping, and you just have to bleed the cold water from the line but it'll run forever once you got hot water to you, but they are designed for a higher temperature jump per flow than a regular one with a tank. I did my house with home run pex, makes it really nice because you just go to where all the piping is and valve out exactly what you want to and nothing else.