This spool is compatible with the Aqara blind driver and should provide a fairly snug fit onto the motor output shaft. The driver appears to provide enough torque to raise roman blinds.
Will work with a pull string up to about 1m long.
I printed mine in white PLA with 0.1mm layers, 8 walls, 4 top and bottom layers and 20% infill. Should print very easily on its back with the channels facing upwards, as the overhang is only approx 45 degrees.
Edit 18/10/22: Added Spool_Alt.stl with a slightly larger diameter hole for the motor shaft
The author hasn't provided the model origin yet.