Eberspacher or Webasto do not supply a 60mm ducting 90 degree elbow connector, they state that such a sharp radius can compromise air flow within long convoluted ducting routes - If your ducting system isn't long and doesn't have any existing sharp radii in the circuit then you could try the below combination as an alternative - see attached image also
Requires 2 x components
Heater outlet elbow
ducting straight connector for 60mm
https://www.butlertechnik.com/item/Webasto/60mm-straight-air-ducting-connector-9009258B-1320469A/59K