There are quite a few papers available in US Arch D (24 x 36 inches):
Canson: Rag Photographique, BFK Rives, Arches Velin Museum, and Arches Aquarelle.
Hahnemühle: Photo Rag. Photo Rag Bright White, and German Etching.
Museo Silver Rag, Portfolio Rag, and Textured Rag.
They are all excellent papers. Just buy sample packs; I can’t see how anyone else can decide for you.
Moab also has some 24 x 36 inch sheets, and Moab and a few others occasionally have A2 paper.
Brian A