E-Mail subscription pop up when clicking button?!

I have been tinkering with this to long and googled, youtubed and searched for answers but I seem to be blind.

I want a beautiful pop up where my users can sign up for our newsletter when clicking on a button on a post.

There only seems to be pop ups available when loading a page, exiting and so on.
Using the mail chimp form on a post fucks it up.

The subscription box is far to the left and not centered, fucking the site up.

I would love any help available!

Thanks

/ Grob

you could try this a free plugin https://wordpress.org/plugins/anything-popup/