Random user agent

Random user agent add on does not exist on this app, I’ve been trying for 3 days to find a way to install it but nothing is working. Why?

This one, the most popular and even with a recommended badge has in the description:

  1. There is an option to randomize user-agent strings.

I haven’t tried it but it looks like what you are looking for.

Okay, thank you so much for your help.