You might get away with making a small boat based on a large Carpet of Flying. A 10x10 flying boat (or tweak it a bit, so it's a boat-shape; perhaps 12x8: 96 square feet vs. 100 square feet for 10x10 - close enough), with a carrying capacity of 800 lbs (1600 lbs for reduced speed of 30 ft - if a party of four 150 lb characters each has 250 lbs of equipment, they can all still use the same boat, they will just be a little slower than one unencumbered). It's power level would be a little less than that of a Carpet of Flying (can't roll it up for getting through tight quarters - unless you include a Folding Boat style enchantment), so you would be justified in either upping the power level a little (1,000 lbs 40 ft / 2,000 lbs 30 ft rather than 800 lbs 40 ft / 1600 lbs 30 ft, say) or reducing the cost a bit (50,000 gp rather than 60,000 gp, perhaps).
Of course, you could also make the "Ship" aspect a special effect, and make it a "folding flying boat" for the same cost as a standard 10x10 Carpet of Flying (60,000 gp).
Either way, very useful for long-distance travel, as it can hustle with no penalties over long distances (it moves "as if affected by an overland flight spell of unlimited duration", and overland flight removes long-distance hustling penalties), probably carrying the entire party and equipment.
