Topic: Signed GameCube - no CoA, advice please?

I have a GameCube signed by Shigeru Miyamoto in London, February 2003.
I was looking to get it valued but because everyone's saying there's no CoA it's only worth £15!
Is there any way I could obtain a CoA? Is there any reputable place I could go?
Many thanks,

While i can't point you to anywhere specific, there are companies that authenticate signatures/autographs. If you can get one of them to authenticate the signature, while it's not as good as an original CoA, it's pretty close.