I've never actually seen one in that color. It is a rare color. Add to that, 2015-2016 only saw 3,000 Z4s in the USA. Of course that includes the 28i. By 2015/16 I suspect nearly all of the cars were DCT and not manual. Best of luck to you, though!
They do exist, though. Here's a 28i DCT M-sport version:
https://www.autotrader.com/cars-for-...ngId=467042307
Filippo