They are much rarer than the standard GC. They are very rare, I have never found a photo of them online, nor found anyone who has any, except for Holderread.
They're called Miniature Golden Cascades. They were developed by Dave Holderread, who is also who I obtained them. They are a tiny bit larger than a Call, but the females can lay up to 200 eggs annually, more than any bantam duck out there.