Hadrien Cambazard, Nicolas Catusse, Fixed-parameter algorithms for rectilinear Steiner tree and rectilinear traveling salesman problem in the plane. European Journal of Operational Research 270(2): 419-429 (2018)The order picking problem is a closely related problem where the products or orders have to be collected in a rectangular warehouse in the minimum amount of time. It is currently a major bottleneck in supply-chain because of its cost in time and labor force. The problem can be solved very efficiently with the same algorithm  that is also available for download on this page.
 Lucie Pansart, Nicolas Catusse, Hadrien Cambazard, Exact algorithms for the order picking problem. Computers & OR 100: 117-127 (2018)
Note that the softwares are distributed for research purpose only and the license prevents any commercial use: License