There is a original Z28 holley Carburetor Fuel Line with the bracket stamped with Stamp Rite listed on EBay now, the item # 151303279793.
The seller had an auction in progress a week or so ago, for a 992-dated 4053 carb complete with the fuel line, y-block and the carb stud support & screw. Made no specific mention of the fuel line support in the description. I was watching it closely to see what it went for. Got bid to ~$150 and then was ended early, reason given "there was an error in the listing". I'll bet someone either tipped the seller off, or they did some research after a question was asked, and realised those parts were desirable on their own; seller now has the carb and fuel line listed separately, and support is described in detail, including the 'STAMP RITE'. Listing also says: "From what I have been told, this setup is extremely rare and tough to find.
As a frequent ebay seller myself, it's fair that the seller realised what they had (by whatever means that occurred) and hence won't part with it for a low-ball price. But as a lover of our hobby, I hope the final price is fair and it sells to someone who will put it on their car, and doesn't get bid to ridiculous levels by the big money-men, or flipped for a fat profit shortly afterwards.