Its a simple 9" measuring device resemblinga standard ruler with notches, spike markers and a 1/8" hole. It probably can be done if you know STL. Do you have a 3D printer? How much do you charge for single color design and printing for say, 40 items?
You dont create STL directly, but rather design the part in some CAD software like AutoCAD, solidworks, sketchup, freecad, or openscad and export the part as an STL object which can be sliced by 3D printer software.
Sorry, I dont offer this as a service but if you can find someone to create the STLs, you can have them printed and shipped to you by a number of online services.