Based on this product's specifications, here are some alternatives and similar models
InLine ISDN Spitter 1->2 InLine 69933
Summary description:
The InLine ISDN spitter 1->2 allows you to split one ISDN line into two, featuring 1x RJ45 male and 2x RJ45 female connectors (8P8C). With a compact length of 0.15 m and a sleek black design, this device is perfect for efficient ISDN line management without resistors, ensuring a reliable connection for your devices.