Original 22B parts are rare as hens teeth, your only option might be to go to a subaru dealer, with proof of ownership (not 100% sure exactly what paperwork they require) and see what they can get hold of, be prepared for a massive dent in your wallet though. Wings for example are about £2k a pop :o although i realise its not wings your after.
Other place is possible https://www.importcarparts.co.uk/