Swim suit for plus-sized 8 year old girl?

My daughter is 8, 9, in a month, and is very particular about what she wears.

Her wardrobe basically consists of Lula Roe women's small leggings during the cold months and loose-fitting fabric shorts during the warm months. She never wears long-sleeved shirts, always preferring to wear short sleeves and a hoodie or jacket as she gets hot easily.

When she wears her pants, she does NOT like wearing them at her "natural waistline," instead opting to wear them at the belt line, similar to how a man would wear his pants.

We don't scold her for her feelings on clothing, and we gave up trying to fight it a long time ago - we just want her to be comfortable and happy.

However, sometimes it makes shopping difficult for us. Our big issue right now is finding a swimsuit for her that fits comfortably and is appropriate. For size comparison, she's wearing Women's Medium graphic tees from Target, and size 18 PLUS (specifically) shorts from Walmart most of the time. The bathing suits we 've found have all been 16 or below for kids, so they're uncomfortably tight. The ones for adults are all inappropriatly cut, with a back that basically shows her whole butt to the world.

She'd prefer a one-piece suit, as she hates the feeling of a seam or elastic on her stomach (hence wearing her pants at her belt line). The go-to so far this year has just been putting her in underwear-style swim bottoms, shorts, and a dark t-shirt, which has worked but I can tell she's not comfrotable. And when she goes to pool parties with her friends I'd like her to feel more confident around others.

Has anyone had experience similar to this? Any advice? Any brands you recommend, or specific suits?

Thank you!