Low-Detail STL Prototype Model

IMAGE UPLOADED UNDER FILES OF PROJECT I already have a rough design for a small prototype and simply need it turned into a watertight STL that my desktop FDM printer can handle without edits on my end... (Budget: $10 - $30 AUD, Jobs: 3D CAD, 3D Design, 3D File Scaling, Slicing & Print Preparation, 3D Modelling, 3D Print Design, 3D Rendering, CAD/CAM, Solidworks)