Perfect for a retro build is this D-Link DWL-G520M Wireless 108G PCI Adapter features 2XR, MIMO technology with a Smart Antenna for improved wireless connectivity. it's a full working device though you will need to find the drivers online. I will post this with the install disk if I have it. Shows signs of use as it's 19 years old but has been in the same system all this time.
eBay