You can see all of the important connections in the cooling loop here:

On the left is a 500L/h pump with a built tank.
https://www.amazon.com/gp/product/B00VHPADRW

The silicone tubing is undersized for the pump connections, but I was able to force the tube into the connectors (rather than over). To stabilize and further seal the connections larger latex tubing was stretched over the whole thing and zip tied to lock everything down.
https://www.amazon.com/gp/product/B013SYAVIU

No doubt this restricts the flow - although it still works quite well thanks to the over-specked pump.

The upper pump connector feeds the print head assembly, then the hot returning water goes into the radiator. The radiator is sandwiched between two 120mm fans to ensure sufficient airflow.
https://www.amazon.com/gp/product/B00CFDS3JA
https://www.amazon.com/gp/product/B000O8I474

The cooled water exits the radiator and re-enters the pump through the lower connection.

I repurposed one of the fan outputs to control the cooling system. Both the pump and the fans run on 12v, but the rest of the system is powered by a single 24V supply. The Rumba board includes a fairly powerful 12v switching regulator - but this seems to have been intended to only power one or two fans. Rather than risk it - I configured the Rumba fan output for 24v (this is a jumper setting) and connected that to a small 12v regulator. The pump and fans are then connected to the regulator.
https://www.amazon.com/GERI-1-25V-30V-converter-Constant-Adjustable/dp/B013WKRDKE