regtransfers.co.uk has SPA 880W on their books, but they want 8 Grand for it..
I don't know of any private reg companies that don't deal with the earlier or Suffix type plate where the last letter denotes age of vehicle but it may not be obvious from their basic search page. Try Advanced Search. Or ring them.
As per the previous post you will not be able to use this reg on a Manta A as you cannot make the car appear newer than it is.
Have you tried the DVLA direct? If the exact plate you want is available, they will issue it and put it in public action. They will also notify you when the auction is taking place. I got mine this way.