You will need about 45of KNO3 and suggar mixure. Expected impuls is 38N*s. I recommend you to print it with PETG because of its better temperature resistance.
UPDATE: First egine exploded (again) so I edit the design and uploded a new version but i didnt test it yet
UPDATE: I test the new design and it works! Only problem was that the specific impulswas too low (about 16s)
Video from test:
The author hasn't provided the model origin yet.