DD is 9. She has a bit of a belly - she's slightly overweight but part of it is definitely also food intolerances and bloating we're trying to get to the bottom of. I don't think it's an issue and we can all see that her belly is getting smaller as a result of a combination of slowly slimming down as she grows and getting on top of the food issues. But she is a bit self conscious at times. She doesn't want a bikini (and frankly, I don't like bikinis on little girls either so that's a win win) but she would like a two piece to feel a bit more grown up and also, because she's a practical child and finds it annoying going to the loo when she's wearing a full costume or even just getting it on or off! 
Surprisingly difficult to find and we absolutely probably should have looked earlier. I've found this one which I think she might like but I'm a bit worried that with her body shape it might sit oddly. I've tried a few of the obvious sites like Next and John Lewis but keep getting very babyish styles or ones that are more on the bikini side vs tankini side.
has anyone got suggestions?
For reference, most of her clothes are from Zara (her spiritual home apparently) and she usually wears a size 10-11 there.