Hey,
I've created a 3D model of Twingo central vent.
It's fully movable to the right and left, and obviously up and down.

Fit in original spot, yet it's far from perfect, covering whole opening for vent. It's quite tight, so it won't move on itself.
I was unable to find the original or replacement part, so I've created this one, and it's working fine for the last 2 years.

The inside part fits in latches in the outside part and won't budge on itself.

Edit:
Added V2 version with horizontal split to direct air more precise.

Use as high quality as You want. It's all up to You. Just make sure to use ABS or at least PETG, as temperature inside the car can go quite high in summer.
I've used 240 nozzles + 75 bed.
40 m/s print with 20% infill
3 layers of wall, top and bottom thickness.

Edit:
I've printed the inside part with PETG, and it's holding fine at full blast heating.

Thanks!