Hi, Wanted to try and step in to help.
Nobody makes an adapter to plug "in" to that radio, and to be honest i am not sure what you would need one for. I can detail what each wire/color, location, and function in that connector if it would be helpful, but you're not going to find anyone that makes a 28 pin plug that will work going in to that radio. Basically that connector is for steering wheel controls, BT mic, CAN High/Low, reverse input for the backup camera (but not the camera itself, that's the 24 pin connector).
The GRAY connector is for the USB. the 24 pin connector is for the backup camera and parking brake. The white one on the far right is for the FM antenna. The 6 pin (2nd from left) is for the rear speakers and dimmer, and the far left provides power/acc/ground, power antenna and front speakers.
Having said that, again, i don't know what you would need an adapter plug for. That radio will really only fit in the 2014-2015 Corolla since it has a vehicle-specific face plate and the dashboard is designed to accommodate that radio. You're not going to be able to put that radio into any other make/model of vehicle.
Please let me know how i can help and i will be happy to send you any information you may need. :)