Available in a number of bore sizes, EPT Excellent Products offers one split shaft collars, 
Indefinitely adjustable and simple to remove, one-piece clamping collars are usually used on hard or smooth standard round shafts, more than a split hub or upon thin wall tube. Through the use of friction to supply superior grip on bars and shafts, one split collars offer sturdier, more dependable results in comparison with the set screw style of solid collars. In addition they offer tremendous axial power, while minimizing shaft distortion for superior performance and decreased wear and tear.
EPT’s stainless and black oxide solitary split collars work very well on just about any shaft. They’re also long lasting, cost-effective and incredibly simple to use: basically slide the collar into placement and tighten the screw to lock it in place.