Down is almost always collected from a live bird or from a bird killed for meat.
There are 3 main ways:
Live plucking, which you seem to already know about. The feathers are plucked from the live birds. This is done multiple times, until the bird is either slaughtered for meat or dies from the process of plucking.
Post mortem collection, where the feathers ...
There are higher end synthetics available that are much better than the regular poly fill stuff you see in average bags.
The two main companies for better performing synthetic insulation are Climashield and Primaloft. Both offer several levels for insulation and some differing technical aspects. Many brands even the more common ones you find in regular ...
Eiderdown is collected from the eider nests. Eiders are a duck that live on northern European and American coasts. They line their nests with the soft feathers from the duck's breast. The original nest material is replaced with straw so the duck can continue to incubate the eggs, or the nest is collected after the ducklings have hatched.
To help you find a perfect match a somewhat more specific set of requirements would be needed, but these should be okay for even low temperatures and should be pretty down like.
Heavier ones (5-6 lbs; 2–3 kg):
Big Agnes Whiskey Park - 0 degrees Fahrenheit / -18 degrees
Marmot Trestles - 0 degrees Fahrenheit / -18 degrees Celsius
Lighter ones (3-4 ...