Audi S3 transfer box


I know this is off piste but my son has an Audi S3 with a leaking transfer box. A new one is £2700.00plus vat and fitting so we are looking for a refurbishment specialist (we live in South Buckinghamshire) but they are like hen's teeth and not only in our neck of the woods but nationally it would appear. My son has tried his Audi forum without much success. I don't know how knowledgeable the S3 forum members (this is not a criticism) are but I do know many Maserati owners are well informed and may have some advice. I would appreciate any help please.