I use QD bumbles stuffed with either a 40cm bamboo square or 2 p'tit dessous inserts. With a blueberry coverall over the top. It can look a bit huge, but who cares at night?
I also got a pre-loved Weenotions Night Notions, which works pretty well and is a bit slimmer, but takes longer to dry.
Junior sounds like your DS - he was 18lb 5 at 6 months
and has chubby little thighs