There is a set of products that Apple has made available for purchase that have not been previously available. When the iMac Pro was unveiled people noticed that the peripherals that come with the iMac Pro match the iMac Pro, meaning that they will be Space Gray. At the time it was indicated that the Space Gray accessories would be exclusively available with the purchase of an iMac Pro. This is no longer the case.
The exact accessories that are available are the Magic Trackpad, Magic Mouse, and Magic Keyboard with Numeric Keypad. These accessories are the same as their aluminum counterparts, however they do cost a bit more; $20 more to be exact. This means that the Space Gray Magic Trackpad costs $149, the Space Gray Magic Mouse is $99, and the Space Gray Magic Keyboard with Numeric Keypad costs $149.
The Space Gray accessories are available for ordering today and ship this week. It would be nice to have a regular Magic Keyboard in Space Gray, but Apple does not make one available for the iMac Pro, so it does not seem like Apple would make a Space Gray accessory available that is not also available for the iMac Pro. Maybe Apple will make a wireless Space Gray Magic Keyboard without the Numeric Keypad at some point in the future, but it may also not come at all.