You will need to install a user script manager extension to install this script.
This script adds a red button in the upper right hand corner of the page that when hovered over will reveal itself and when clicked it will copy your Mturk ID to the clipboard allowing you to paste it. You must edit this script with your own unique Mturk ID. Replace the words "ENTERYOURIDHERE" with your own Mturk ID in the code. An example is shown below.