I have a copper tube feeding water to a humidifier; want to insert a small sol valve so I can turn it off remotely. Any suggestions

 

Solenoid valve. Many different makes and models perfect for the job. I used industrial ones and Asco Red Hat comes to mind. 1/2 in Air, Oil and Water Solenoid Valves - Grainger Industrial Supply

 

I have a copper tube feeding water to a humidifier; want to insert a small sol valve so I can turn it off remotely. Any suggestions

Electrically turn it on/off or manually?
Use the water line intended for an ice maker on a fridge. This semi-rigid tubing fits perfectly into these valves.

https://www.lowes.com/pd/B-K-1-4-in...gChBUWc177QN6sEXJ7xoCKp0QAvD_BwE&gclsrc=aw.ds

This one is even easier, it uses "shark bite" technology - just slip the neatly cut tubing into the valve body and give it a tug to set it in place. No tools.
https://www.lowes.com/pd/SharkBite-...onnect-dia-Ball-Valve-Push-Fitting/1000192681