The Drayman is a heavy Merchant Ship. It has bad acceleration and maneuverability, but also has 10 jump fuel and by far the largest cargo space of all ships, more than 5 times as much as the runner up (Ulysses).
Where to Buy this Ship
For 1.2M available at these shipyards:
Crimson Quadrant
Alizarin Quadrant
None
Viridian Quadrant
Mauve Quadrant
None