My vote for a durable C&V headset is the Stronglight Delta needle bearing headset shown on the left of the pic below:

It has the features of the original/proven A9 needle bearing design but backed up with O-rings at the top and bottom races to help seal the bearings from outside moisture/contamination. It's still very light at 77 grams.
They still come up regularly for auction at ebay in English and French threading. They go for typically around 55 to 65 bucks NOS. They sell quick as they are still very popular with C&Vers, just like the A9s.
the one on the right in the pic is the Stronglight model JDX94 needle bearing headset. I think it came out around the time Stronglight was providing integrated headsets in the early 90's to French companies like Vitus for their bikes. The interesting feature on this headset is the upper bearings and races are flipped upside down from how they are in the A9 and the Delta. The concept was to provide a more stable reverse thrust effect from above to locate the steering tube in the headstock. It features a moulded in delrin locking bushing in the upper crown (black band at the top portion of the headset) that cancels out the typical top locknut you find in traditional headset. unfortunately, id did add some weight to the design coming in at 111 grams.

Chombi