Best plugin for a "Try now!" button?

Hi,

my agency wants a template that’s a design similar to this one: weclapp.com , but in particular wants the “Jetzt Testen” (Try now) pop up button, with a direct connection to a customized register form.

I’ve checked tons of pop up plugins but I didn’t find one exactly with this function -or customizable enough for my purposes.

Any idea on which template / plugin I can use in order to achieve a similar result (both visuals and functional)?

Thanks a lot