Welcome to BYC! Despite what many "chicken experts" say, there is a such thing as a large Silkie. However, I read they are common in Australia, like bantam Silkies are in the U.S. (and probably the U.K. too). I'm not sure where you could get any though. Have a great day!
I'm an Aussie and can say we do not have giant silkies (as far as I know), and agree with drumstick diva that their size is a large part of their charm. (sorry if I ruined your hopes and dreams)