Type of spanx to wear to flatter my tummy and butt

Hi ladies! I have a mermaid dress that I am absolutely in love with from BHLDN. When I first bought it I ordered it based on what the woman at the store told me to get (based on my measurements). However, I tried it on recently and it fit everywhere perfect (except my butt lol). It was so tight on my butt that I couldn't sit down, so I switched it out for a bigger size, which I know will mean more alterations will need to be done but oh well, it had to be done! Now I want to make sure that during the day I am not looking down at my tummy to make sure it is still flat, despite me eating and drinking. With that said, my question is that I want to find a pair of spanx that will flatten my tummy and still flatter my butt- does anyone know of an exact name of spanx that does that? Because part of what I love about my dress is the way it enhances my butt and hips (but it would be not to forgiving if I got stress bloated or got a food baby lol).