I am currently thinking about a project for making my 21:9 monitor touch compatible. So i got the 34um68 lg monitor with 34" and i alredy thought about using some proximity sensors like the "VL53L0X Time of Flight Distance Sensorhttps://www.adafruit.com/product/3317 " and sending sending it to an arduino leonardo, who translates it over a Serial connection and acts like a mouse, but reconizing the real touch could be hard. Maybe you got some ideas! (the project cost schould not exceed 60$)