Tourist Bus Sim is on sale for -25% on our publisher's website from 19th to 25th August:
https://www.aerosoft.com/en/bustruck/bustruck-simulators/2420/tourist-bus-simulator?c=1139
Of course, after purchase, it will run via Steam and become added to your games library on Steam.
And remember, all vehicle DLC's are compatible between Tourist Bus Simulator and Fernbus Simulator: Buy once, play twice!