Based on this product's specifications, here are some alternatives and similar models
PCIe RS232 Serial Adapter Card 4-port, StarTech PEX4S953, 16950 UART, AX99100, Full/Low-profile
Summary description:
StarTech PEX4S953 is a 4-port PCI Express RS232 serial adapter card with 16950 UART and Asix AX99100 chipset. It provides four DB9 serial ports via a PCIe host interface, supports up to 921.6 Kbit/s baud rate and 256 B FIFO, and fits full-height and low-profile slots. Certified CE/FCC/WHQL, MTBF 214,358 h. Suitable for industrial devices, legacy equipment, POS and serial peripherals on Windows and Linux.