Mini displayport to usb c

I have a Macbook Air at work, which has a mini display port but some colleagues with newer laptops now use usb c, which means I can't connect to their monitors when I'm hot desking. I have been searching for a mini displayport to usb c adaptor (i.e. the opposite of this one!) but no such luck.

Does this really not exist? Or is there a workaround I have not thought of (an easily portable one)?

Any help or ideas much appreciated.