Having had my original old style Windsor/Cinelli seat clamp bolt lost by a painter about a year and a half ago, I launched on what proved to be a saga to find a replacement.
In the end, some other CR members and myself collaborated on a project to have a dozen stainless steel replicas made by list member Fred Durrette, wo has previously made replicas of the newer Cinelli bolts with allen heads. The project participants, including myself, are keeping 10 of the dozen bolts made for our own use, but there are two bolts available for sale to the CR.
These are replicas from an original pattern from a CR member's Windsor Pro and have been installed to test fit on my 1972 Windsor Pro and on a genuine Cinelli. This is the old style bolt with exposed bolt head and nut. The nut is extra long, giving adequate wrench purchase. The nut also has a flange on one end that fit snuggly into the recess in the seat lug. I've seen several variations of the old seat bolt, both on Windsors and geniune Cinellis, and this is by far the most elegant variation I have seen. The bolt head is beveled on the inside so that the bevels seat slightly into the recess in the seat lug on the bolt head side, yet leave enough bolt head exposed to use a wrench on the bolt head without scratching the frame. The oirginal bolt was chromed steel, but these replicas are stainless.
There is one important fact to be aware of. The original Windsor bolt had a 3/8" nut. Not 10mm, not 9mm, 3/8". I have no idea why Windsor chose an English size nut, but that was original and that is what we have reproduced. So if you buy these, you will need a 3/8" wrench.
The two bolts are offered to CR members for $20 each plus shipping. There has been some discussion of Fred producing another batch of these or perhaps a slight variation with a 10mm nut for genuine Cinelli owners who don't own an English wrench set. I don't know that any decision has been made about this, so you should probably contact Fred directly about that.
Big Spring, Texas, USA