Cars not fitted with a CD changer had a cubby hole type insert for a bit of storage, can be quite useful in the e85, which as we know isnt exactly bursting with storage space!
Theres one on fleabay, here's the link.
https://www.ebay.co.uk/itm/BMW-Z4-Series-E85-E86-Rear-Centre-Console-Storage-Tray-Cubby-Black-51467043819/223442586477?epid=1587393753&hash=item3406374b6d:g:VBQAAOSwmwFchRcj
Edit - I'd check the part no, as the top and bottom one are different sizes I think.