I am currently developping a customised fan for a Jetson Nano application.
While looking through the official documentation, I understand from NVIDIA that the J15 connector has a 1.25mm pitch between two consecutive pins.
Digging further from the jetson nano carrier BOM, I recovered the connector part (2WBA2542WVC-F-04PNLBT1N00G) and while looking on the manufacturer website with I found that it is a 2.54mm pitch