Simple postcode popup on click add to cart

Hello,

I was searching after a simple module that would popup a window onclick Add to cart button so a customer can provide their post code due to estimate shipping costs.

I have seen a lot of advanced modules but non of them seems to work/pop up on action (button click).
The module I am thinking about would mostly do the same job as default estimate shipping on cart page.

Anyone that have found something I am looking for?