Why not have a US frame builder build you an audax (or sports touring) bike? Jackson and Mercian are fine builders but you are buying from overseas which will make it much more of a headache to warranty the bike if you have any problems. Gunnar makes a stock sports touring frame that should be close to what you want. If you want to spend more, I've always liked Waterford bikes. In any case, the list of frame builders in the US is pretty long for a custom bike.