Update: thanks to Ikea Hacker for the love!
I was refinishing a six Ikea Gilbert chairs with fresh paint and polycrylic when I noticed that I was missing a few feet - they must have popped off over the years.
I went to my local Ikea, but they don't sell these chairs anymore, so the replacement parts are sadly no longer available! ...until I created a 3D model and printed up a batch of fresh chair feet.
They are a little tighter than the originals, which I'm hoping means that the replacements will be less prone to popping off.
Next, I need to paint the replacement feet with a touch of black paint. ... or, one could just print them in black ABS, or go for a splash of color instead.
I published the design to YouMagine (an object design repository) for anyone else who wants to repair these awesome modern chairs.