Logitech Webcam
This is the one i have - https://www.amazon.com/Logitech-Laptop-Webcam-Design-360-Degree/dp/B004YW7WCY
To do it for free use a webcam app for your phone and mount the phone on your monitor. http://ubuntuhandbook.org/index.php/2015/01/use-android-phone-as-wireless-webcam/