Based on this product's specifications, here are some alternatives and similar models
Threaded Connector PARTNER PA-FF06/06 — internal thread 3/8" x 3/8"
Summary description:
PARTNER PA-FF06/06 is a threaded connector with internal 3/8" x 3/8" threads designed for joining two compatible threaded fittings or hoses. The part provides a compact mechanical connection where identical female-threaded ports need to be coupled. Suitable for plumbing, pneumatic or hydraulic applications that use 3/8" internal threads and require a straightforward, space-saving coupling solution.