I live in UK and have recently been having same concerns. I am 47 and posted the "age of first TKR and multiple revisions" entry.
I was contacted by someone who has had the Smith & Nephew Oxinium in Liverpool who recommended it, and I have found a consultant in London who uses that knee so it is available over here!
In my case the consultant has decided to do a further debridement and to try and burr away some of the oestophytes, hoping to delay the replacement a few more years as I have a little space still on the medial side. However it is inevitable that I will have the replacement as the lateral side is bone on bone, and the Oxinium certainly seems the best option from the research I have done. The problem with the cobalt ones is there limited life compared to the Zirconium ones.
I am going in for the arthrotomy next week and hope it will delay the inevitable at least two years!