If you're willing to jump through a few hoops, the confines of international shipping don't have to apply to you. And you should be willing to put in the extra work because Japan makes some of the finest clothing in the world, particularly when it comes to Americana and outdoor apparel.
This corporatized proxy is extremely easy to use and has one of the lowest fees in the market. Excluding shipping, you'll be charged $4 per item plus 9.9 percent of the item's total cost (or $8 if the total isn't higher).
This proxy is less buttoned-up, run by a husband-and-wife team who maintain the namesake webstore out of Japan. That'll make your interactions more personal, but Stylistic's fees are also slightly higher at 10 percent or ~$19 (whichever is higher).
Zen Market is dumb cheap, with a fee of only $3 per item. And your first purchase will essentially be without fee, as signing up for an account comes with 300 yen free. You do, however, have to make a deposit that'll increase if you use a direct bank transfer.
Buyee Japan, which has a relatively low fee of $2 plus 5 percent of the item cost, is more useful for Yahoo! Auctions because of its limited list of sites it'll work with it. But it's worth including here because Yahoo! Auctions rocks.
The Japanese equivalent of eBay is a gold mine for bargains. There you'll find new and used apparel for way cheaper than you'll find here in the states or straight from the source. It's a wormhole you may get upset at me introducing you too, but can ultimately upgrade your wardrobe in a way you never knew was possible.