You want something like these:

http://koolance.com/ins-fm16-coolant-flow-meter

They have a link for the fittings, depends on what size tubing you will use (they also have tubing).


About plumbing, to avoid corrosion:

Do not use aluminum with bare (unplated) copper or bare (unplated) brass in the same system.
Do not use silver with nickel in the same system.
Robert