There aren't many models for spades out there. I started to model my own with the idea of using this rectangular section design. When it came to modeling a handle I just decided one really wasn't necessary.
This can be printed without supports, and if oriented as pictured ( in the second photo with the shovel opening on the bed), the layer lines will be oriented properly to handle the forces applied when shoveling.
The author hasn't provided the model origin yet.