I think the white Up you have pictured has Thule roof bars and the owner has then found a suitable " box " to bolt to the bars. I cannot find a roof rack as such either for the Up. keep looking though as I,m sure you will find something that will accommodate your camping gear.
I found it.
It's a bit prices but basically you have to buy the Thule roof bars, then the basket from Thule, specifically 'Thule Xperience 828' which is around £200ish mark.
So all in all including the bars it'll cost about £300.