You never want something until you can't have it. So, each week in The Sell-Out, we're getting the scoop from your favorite retailers on what's selling like crazy. Watch this space to find out what everyone's buying, sign up for wait lists, and keep tabs on restocks.Why is it that every time cold weather hits, it feels like we end up buying a whole new wardrobe full of sweaters before landing on the one; you know, the one that's ultra-cozy, completely versatile, not itchy, and not too boring — all at the same time? That magical knit isn't always easy to come by, either, which probably explains why this pretty-much-perfect turtleneck from Reformation is selling like crazy.This particular relaxed-fit sweater falls just below the hip, and works just as well underneath a denim jacket as it does with your collection of dresses, skirts, and heavier coats. It has that perfectly oversized look (without having to size up), too, and is made from 100% baby alpaca wool — which means it's the kind of piece that will have you feeling extra cozy and warm.But the one thing to note about this cold-weather staple: It definitely won't last forever (nothing at Reformation ever does!). So click on to shop it while it's still hot (and available). And if the stock is wiped clean by the time you're reading this, we've pulled together some alternative options that will help you survive winter just as well.