Solution
These accelerometers are manufactured by PCB Piezotronics and National Instruments only resells them.
You can find the specification documents on the website of PCB Piezotronics:
https://www.pcb.com/imi-sensorsThe following list shows, how the NI part numbers correspond to the PCB Piezotronics part numbers:
Format: "NI P/N" = "PCB P/N"
General-Purpose Accelerometers:
Industrial Accelerometers: