So you want to customize your transmitter. Hiro Seiko has an option for you. They have released 2 new types of Aluminum Steering Wheels, a 7-Spoke and a 15-Spoke. They are available 6 different colors, easy to install these will fit the KO Propo, Futaba, Airtronics, and Spektrum transmitters.
Note: These do not come with an adapter. Adapters should be acquired from the transmitter manufacturer.
For more info check out Hiro-Seiko.com