Sony will shortly launch the wireless charging kit for the Xperia Z3 which includes the WCR14 Wireless Charging Cover and WCH10 Wireless Charging Plate. Sony uses the Qi standard for wireless charging, so any charging plate should work. However, Sony is offering both items in one package for around the £60 mark in the UK.
Some places do have stock, for example third-party sellers on Amazon UK. Others have already sold out of their initial stock including MobileFun and Clove. If you want to see the two accessories in action before pushing that buy button then check out the video below.