>"you found a Sierra Designs down jacket in a thrift store?"
Oh, it happens. I've scored that and better many times. Whether I'm looking for a dress shirt or kid's puddle boots, or whatever, I look at labels. Dress shirt example: LL Bean, Nordstrom's, Land's End, etc. Jackets: Sierra Designs, Northface, Patagonia, Helly Hansen, etc. Only when I see a quality manufacturer, do I slow down and look at condition, size, etc.
It helps to be shopping for a family of growing kids so there are many more possible sizes and many sizes that can be set aside for a year or two. Also, quality kid's stuff is outgrown before it is worn out.
But the best, easiest deal? Kiss up to a family with older kids. We hand off a lot of great stuff to local friends.