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.Topshop is every fashion girl's go-to for on-trend buys that won't totally break the bank. It's the one retailer most likely to get you the question, "Who makes that dress/coat/shoe?" when people mistake its items for high-end designer duds. And, don't even get us started on its shoe section — the Topshop sea of Miu Miu-esque platforms and effortlessly chic Chelsea boots is just shy of nirvana.So, we weren't surprised to hear that its perfectly mod silver Chelsea boot is selling like crazy. Our friends at Topshop say the boots already sold out completely, but have just been restocked online — so you better make moves, quick. And, if you'd rather try them on, we've got a little secret: The initially online-exclusive boot will be hitting stores next week. In the meantime (or if Topshop's pair is already sold out by the time you read this), click ahead for similar picks that will majorly up your boot game this fall.