Recirculating pump/system for Rinnai Tankless water heater

[PRam]

We installed a Rinnai Sensei Ru180eN tankless water heater. However, the 2 bathrooms that are a little far away from the heater take a while to get hot water. After some research we are thinking of adding an external recirculating pump - so that we can save on wasting water. Questions
1. Which is the best recirculating pump that will work with the model of the water heater
2. Do we need a dedicated return line or will a valve in the the sink of the farthest bathroom work?

Thanks in advance!