I recently replaced our old 40 gallon water heater with a new Takagi T-D2U tankless. The unit is mounted on an exterior wall. One of the expected results of this is that there is now a long wait for hot water in our bathrooms. The old system had a re-circ loop that is capped off for the time being. Direct line it is about 50 ft. from the new tankless to the farthest bathroom. I do not know the overall pipe run length under the house.

I'd like to install a new re-circ pump that is compatible with the Takagi. Models with a timer/aquastat are preferable to push button. According to Takagi, "the only requirements we have are that it needs to be able to push minimum 2gpm, maximum 4gpm through the system with 1/12hp."

I'm having a hard time finding the right model that seems to fit within the requirements.
Any recommendations on a pump that fits these specs?
Are there any that can be mounted outside next to the Tagaki? If not, I suppose I could put the pump in the laundry room right where the old re-circ loop is capped at the moment (about 20 ft from the tankless).
As an alternative, I know there are systems to go under the faucet at the end of the line. Any pumps that would make sense for this? I've seen some that would allow me to abandon the re-circ loop entirely, but do not know if that is a good idea.

Thank you very much!