As a European, haven’t you heard about the existence of the B and C series of paper sizes? It may not be exactly what you have in mind, but B4 paper is 250 x 353 mm (9.8 x 13.9 in) and C4 paper is 229 x 324 mm (9 x 12.8 in). There’s also elongated A which is really long.
I hope you appreciate the irony of an American telling you about them.