Nyan Cat Spacebar Keycap for Cherry MX.
The current spacebar model should work fine for most cases. However, the design model has been included as a separate STL for those wishing to make your own custom versions.
The easiest way to print your own version would be to use the slicer software (i.e. Cura) to position the design model on top of an empty spacebar model.
As for getting an empty spacebar model, I recommend using rsheldiii's OpenSCAD keycap model generator from ThingiVerse: KeyV2: Parametric Mechanical Keycap Library. This is a fantastic library that facilitates the generation of keycaps of any shape and size as well as adding supports for easier printing. I included a modified copy with some preset parameters for convenience.
OpenSCAD is a free software that facilitates parametric 3D modeling. If you are unfamiliar with OpenSCAD, I really encourage you to try it out. Just follow these steps to start generating your own custom models:
The author remixed this model.