I will provide exported STEP files soon, alongside the STL files. I used Solidworks not only because it's the standard in our research lab, but also because I couldn't do what I wanted with any other CAD package. My source files are actually highly parametric, with extensive use of a set of global variables to help me adapt the designs for different printer settings and different system design constraints without having to rebuild the CAD every single time. The closest open-source solution I could find with similar functionality was OpenSCAD, but (imo) it's not mature enough to handle assemblies or more detailed models, and I'd bet that far fewer people have ever tried OpenSCAD than Solidworks.

If you can suggest an alternative open-source CAD package, not just file format, I'd be happy to look into it. Thanks for the interest!