Looking for a specific floating button

Hello All,

I am looking for a floating ‘sticky’ button.
I’ve attached two photo’s of what I mean ( bottom right on the photo you see the yellow button )

I want an unfolding button that people can press on when they are interested for a specific item.
Ideally it works with a ‘post_url’ tag so that I can see what people are interested in when they decide to fill in one of the choises. So that when they decide to press e-mail, that they don’t have to manually type what they are interested in.

Hopefully it is clear and you can help me.
With best regards,