Hello Lorenz,
There are no step files for the NXP boards. There are some mechanical drawings with the board shown in 2D, which are not publicly available, but you may inquiry for them through a support ticket, but it does not have all the dimensions you would require to have a 3D model.
Most of the times customers take the actual dimensions from a combination of direct measurement of the board and gerbers/layout files.
My apologies for the inconvenience.
Regards,
