I would NOT suggest the Medium Absorbency+. It is 37" long, one of the highest rises for a Medium sized diaper.
small Dry 24/7 would be a good choice.
Also, I would suggest trying NorthShore. They have a youth diaper. I haven't tried it, and honestly haven't heard great things about it, but it might work for you. They have an AirSupreme brief in a size small that would be a good choice, if you don't mind cloth backed. They're a great diaper, and the best cloth backed I've seen. If you call NorthShore or chat with them on their website, they will send samples of two products to you for free.
Another thought might be Tranquility. They're not as good as Dry 24/7 or AirSupreme, but a step up from what is found in stores. Their plastic backed diapers were all white except for the wetness indicator, the last I knew. Be aware that a large part of the padding is a distinctive orange color, instead of white or blue. Their youth diapers aren't any bigger than baby diapers, but the size small might work. They sell samples on their website.