The feet are held with 8x1.25 mm threads that made replacements hard to find.
Even at Hartville Hardware (world's largest hargware store), the best I could find were the round headed bolts in the center. These gave me adjustability with a wrench, but had a small, hard footprint.
I noticed the feet that Paul Chasse (Astronewb on CN) had on his tripod and wrote him. He had found a source and provided me with three for $30. You can see this one on the right.
These feet provide a larger, sure footing on soft ground and have rubber pads on the bottom to dampen vibration on hard surfaces. I find that I can lift a leg slightly and rotate the foot easily by hand. Each turn moves the foot 1.25 mm, which provides fine adjustment. I rough adjust by adjusting the tripod legs and fine tune with the feet. It's a big improvement over the stock feet.