What are some good harnesses for a first time walking, BIG kitty? (Talking over 16 lbs and wide)

Looking to get my cat into walking and traveling. She’s a big gal though, shes hovered between 16-17 lbs despite my diet based efforts. She’s especially wide around her shoulders and upper torso too rather than just a big belly. It’s also worth noting that she wears a collar, in case some harnesses make that cumbersome around the neck.