Yutai Optics offers a lot of half balls to European and American customers, the material range from BK7, fused silica, sapphire and ruby, as well as other optical glass.We may have some similar stock half balls for your project.
Diameter Tolerance:+0.1, -0.1 mm
Thickness Tolerance:±0.2 mm
Clear Aperture >85%
Surface Quality:60-40 scratch and dig
Coating :Specified by customers