Best night time pull up nappy for 4 year old

[thejaffacakesareonme]

DS is 4 and still wears a nappy at night. He is skinny and weighs only 36lb. He produces some amount of wee though and I moved him up to size 6 pampers pull ups in the hope that they'd hold the wee. They don't. I suspect that it may be leaking out the top and the leg holes. He wants to wear a pull up so that he can be a big boy. Any ideas for something that may fit a skinny 4 year old?

We had a skinny 3.6 year old in night nappies (he was dry after that). We found the very best to be Pampers UnderJams. They're bloody expensive, and actually designed for rather older kids I think, but they never, ever leaked (unlike normal pull-ups, which we had real trouble with).