When I got to my destination, there was such a variety I regretted buying the ones here.
I suggest you get the basics to get you there in one piece, then enjoy shopping for good winterwear in good fashionable styles.
About WinterWear, it is definitely pricey but I got a really good coat that came in a pretty unique design/colour. In the hostel where I stayed during my trip, it apparently got a nickname as "THE coat" -- everyone including the staff had taken notice of my famous purple coat! That's the perk of shopping here, having something no one else has over there
Oh I've just gotten into a bit of a shopping frenzy looking for shoes online in Singapore, and they have a really good range of other stuff including winter coats. So sharing the love. I don't know how weather proof they are but they've got leather jackets and wooly parkas and stuff. Man I wish it were cold enough here so I can jump into the winter fashion haha. (well we do have mad airconditioning...)
So far, the best shop I've been to here, is Winter Time (Citimac main outlet). Since the OP is headed to Japan, I'm not sure if prices will be cheaper there, but definitely there's going to be more style and variety. So, a better bang for your buck. For those heading to Europe, my experience tells me to get the stuff there. Mango, Zara, H&M... all are cheaper and nicer. Beware though that these fashion chains are not the experts, so their stuff might not get you through snowy sub-zero conditions.
to the nice folks cause you are outta here!