Follow up with actual files and pointers.
I can recommend this one from the ACES community, has pretty much every gradient you might think about:
syntheticChart.01.exr (16.9 MB)
I have made some using Blender as well. Both Eevee and Cycles output scene-referred data in rec-709 if you save as .exr
Its possible to construct pretty advanced charts using the “Emission shader” and some other nodes!
Example blend-file:
color slice.blend (667.7 KB)
Example exrs that I have generated:
inside cube.exr (5.5 MB)
glare triangle bloom.exr (21.7 MB)
And finally with Python:
I have used imageio to save numpy arrays as exr:
imageio.imwrite('chart.exr', chart_np_array)
Example exr:
color_wheel.exr (983.8 KB)
Hope it helps!