Its very simple process.
On weekends engage your husband in activity of clay art preparation. Make a clay ball and ask your husband to help you. He will ask "how" then tell him to press the clay ball till you not say stop. He will as many questions tell him this is an abstract art idea i have came up with and see the clay ball being pressed till you see the ring finger is nearly embedded in the clay now slowly remove fingers from the clay you will get the approximately 95% accurate ring finger diameter or size.
next process is make a clay wheel and tell your husband to put his ring finger to the end in it this will pull a hole in the clay wheel in th middle and then put it to dry it will give you some 95% accurate ring finger size
If you find these process useful let me know also if you need more process you are welcome