No Duvets for under 1?

We use feather doonas for both the boys. They're single bed size so they tuck in thoroughly. When they were NBs I swaddled them and used cotton and wool (though I see that wouldn't be an option for you) and a quilt the had the squares stitched in so it wasn't poofy. When they were 3-9mo they were swaddled in a sleeping bag (we swaddled for ages because both the boys slept better that way!) with a feather doona, then when they were unswaddled it was a merino sleeping bag under a woolen blanket and the doona so nice and snuggly. We use huge blankets though so it all gets tucked in thoroughly then if they're sleeping all over the place I use elastic with clips to clip everything under the mattress so they can't kick their blankets down or get them up round their faces.