You can buy from Yupoo, Weidian or WeChat on Cssbuy through the Quick Buy page. If the automatic Taobao order filling is down you also have to fallback to this page.
Fill out the fields:
Item Url: Yupoo/Weidian Link
Fill title: Name of the item you want to buy
Note: Enter the size and color of the item. For Yupoo orders you should also enter the sellers WeChat name, and your own if you had a conversation
Price: the item price in CNY
Domestic shipping: the domestic shipping fee in CNY
Quantity: How many copies of the item you want to buy