Based on this product's specifications, here are some alternatives and similar models
Noctua NA-FD1 computer cooling accessory — steel ventilation duct kit, 16 spouts, 4 screws, 7 washers, 5 mm spacers, height 5–45 mm
Summary description:
Noctua NA-FD1 is a steel ventilation duct accessory for compatible low-profile CPU coolers. It features 16 spouts, includes 4 screws and 7 washers, and comes with 5 mm spacers. The duct supports installation heights from 5 to 45 mm and is designed for compatibility with NH-L9i, NH-L9i chromax.black, NH-L9i-17xx, NH-L9i-17xx chromax.black, NH-L9a-AM4 and NH-L9a-AM4 chromax.black models, helping guide airflow and improve cooling in compact builds.