Air fuel sensor legacy gt

[Smfit]

Hi all, 

having a problem dropped car off for MOT and they failed on emissions, seem sure it’s the front 02 sensor in the cat, but from what I understand it’s actually an air/fuel ratio sensor. Main problem is subaru Uk arnt being much help and I found the part number but can’t seem to find the part to buy all sold out, does anyone have any ideas where I could get one?? Part number is  “22641AA410”

many thanks,

 

Sam.