You can get perfectly usable ski clothes in any size at places like Kohl's and other discount department stores. I particularly recommend Kohl's - I've gotten very good gear there - base layers (inexpensive versions of stuff like UnderArmor) and fleeces. They also carry Columbia jackets, which, despite lacking the cache (and some features) of high end brands, are perfectly serviceable for skiing. Look for knit gathers at the cuffs and zipper pockets. All of these are very reasonably priced and you can catch them at this time of year deeply discounted as they prepare to move in the spring and summer stuff. I usually look in places that cater to hunters for socks - they work fine for me - again, always get moisture-wicking.
The only real challenge will be in getting a good pair of ski pants - this one is tougher because they are hardly carried by anyone except for stores that cater to skiers. Try the sierra trading post, an on-line retailer that carries close outs and odd lots: http://www.sierratradingpost.com/
You can buy very decent ski clothing that will work very well without paying the prices you see in ski shops.