Hi B Feelgood,
King size Dunlop 3" or 6" cores without any glue seams are certainly available (although you couldn’t ship a single 6" king size Dunlop core through courier because it would be too heavy and it would need to be shipped with a common carrier which is more costly) but the largest continuous piece without glue seams that is available in Talalay is queen size (see post #2 here).
Phoenix