Based on this product's specifications, here are some alternatives and similar models
Chimney Tees WADEX 107 mm Diameter, 200 mm Length
Summary description:
Chimney tee by WADEX with a 107 mm diameter and 200 mm length designed for connecting and branching round flue pipes. Suitable for use in chimney and ventilation systems to divert flue gases or create a branch line. Constructed for installation between sections of ducting; used in residential and light-commercial heating appliance exhausts where a 107 mm flue is required.