Road Cars for Milli - When can you buy the right model? (Gran Turismo Sport)

https://proiide.net/gtsport/category/n500
https://www.gtplanet.net/forum/threads/gt-sport-special-cars-color-variation-list.381851/

The game has a Special Shop that sells Road Cars, paint, rims, etc. just for Milli.


I want to buy some of these models
I like the Mazda Atenza Gr.3 Road Car (Road version)

Most of the cars are for Category N500 and higher.
But here's the catch, only 1 car appears in a certain period.

How can I buy it? What is the timeline for these machines?