Fairly simple, but I couldn't find any decent existing models.

Note that this is not a true stack, since tangential spheres are obviously difficult (impossible?) to print. So, this is just the outer layer of cannonballs with an inner, solid pyramid as the support structure, which I think still looks pretty realistic at small scale.

The base/frame is separate geometry, which can be separated via “split” operation in most slicers, if you want to print with a different filament/color, which I recommend.