Coupon X: Discount Code Pop Up

We use this app to show our page visitors a discount for their first purchase with us.
We had a really hard time to find an app that does exactly what we want, which is a discreet small pop up at the bottom of our page that doesn't force a visitor to interact with it even if they wouldn't want to. Most of the other pop ups that we were able to find were obnoxious and way too big.