Ok! Uhm... I looked through some Wiki articles and now have a list of offers available on ebay.de! Please excuse any doubles!
www.ebay.de/itm/MacBook-Air-13-A1369-11-A1370-WiFi-Bluetooth-Air-Port-Card-BCM943224PCIEBT2-/291245627035
There might be adapters in the list! I am not sure: do they all fit into a full sized PCIe?