The machine shop needs a step file, but OpenSCAD does not export STEP files.
Use FreeCAD to convert the STL file from OpenSCAD to a step file.
Use OpenSCAD to export a STL.
In FreeCAD open the STL file. Using the Parts workbench select Create shape from mesh… from the Part menu. Check Sew shape checkbox and enter 0.01 then click OK. This will make the most accurate shape possible.
With the new shape selected, select Create a copy / Refine shape from the Part menu.
With the refined shape selected, select Export from the File menu. Under Save as type: select STEP with colors (*.step *.stp).
To confirm your STEP file was created successfully simply open the file using FreeCAD.
FreeCAD – 0.20.1
OpenSCAD – 2021.01