The tool is available online and at State Trailer Supply, Salt lake city,
and can be ordered online at their website... Cost - about $10 If you don't see it, Call them. They are great to work with.
Get the tool if you have a Flair-It system. Yes - pliers will work in a pinch but the ratcheting tool (plastic) works on 1/2 inch and 3/4 inch and it does not chaff the fitting with burrs etc. Those burrs make it hard to keep clean and spotless underneath sinks, lavs etc. Don't be afraid that the tool is plastic. It is plenty rugged, doesn't rust, is light weight and compact for any drawer or tool box.
State Trailer also carries all types of Flair-It fittings and adapters. Buy a few spares, 2 couplings and a small length of PEX. I throw all of them in a plastic zip-lock and just leave them under the sink or behind the water heater along with the tool. I never have had a leak. Knock on wood.
https://www.statetrailer.com/