Based on this product's specifications, here are some alternatives and similar models
Compression reducing coupling Comap MultiSkin brass/tinned 26×16
Summary description:
Compression reducing coupling Comap MultiSkin in brass with tinned finish, size 26×16 mm. Designed for transitioning between piping of different diameters, this press-fit fitting provides a sealed mechanical connection for plumbing and heating installations. Suitable for potable water and central heating systems where a reliable reduction from 26 mm to 16 mm is required.