Cinelli used 26.4 MM prior to 1998 and then switched to 26.0 MM diameter.
Shims are available, for sure, to bush most of the old bar clamp diameter standards to a modern 31.8 MM stem. The real question is 'why' bother going that route? Or tracking down those hybrid stems?
With all the modern bars in just about every reach/drop combination known to man and in classic round drop, modified decreasing radius drop. anatomic and semi-anatomic bends AND in ovalized, oversized, flatted, teardrop and who knows what other shaped flats...in carbon, aluminum and carbon wrap...there's bound to be a modern bar for every taste and budget.
Good list OBC!
Alf, I loves me old Cinelli classic bars. Almost every bend was tasteful to the eye, applicable to the type of rider and ring style and just stiff enough. I would not sell any of my spare old bars, but on a modern bike? I'll hit the internet every time for one of the new 'big' bars.
Oddly, the flimsiest bars I ever owned was a 2007 FSA 'Energy' bars. Like holding on to wet spaghetti. They were on a bike I have that had my first carbon steerer and for a while I though I had a flexible steerer.