Just done mine on the Ambo, you have to remove the rivet & replace with the pair (1 each side) from Rare Spares
The new rivet may need the hole in the hinge to be enlarged slightly with a drill
After fitting the rubber to the frame, get a helper to hold the 1/4 window assembly upside down with the top or head of the rivet resting on an anvil so you can whack / spread the underside of the new rivet with a centre punch
Also, there is a small slit in the rubber near the rivet hinge, make sure to slide it over the hinge
When re fitting the assembly to the car
Don't forget the drip deflector that fits between the door frame & the assembly like I did