Wilde branded seat collars to complete the look. Made for us in Minnesota by our friends at Wolf Tooth. They come in two sizes. 29.8 and 34.9

From Wolf Tooth:The precision-engineered Wolf Tooth Seatpost Clamp secures your seatpost and looks good doing it.At the heart of this seatpost collar are our custom self-aligning bolt and anchor. The M5 bolt includes spherical washer and mates with a cylindrical anchor barrel. This means that threads are always perfectly aligned, preventing binding and ensuring consistent clamping force.Machined from 6061 aluminum in our Minneapolis facility.