Electromagnetic topological optimization holds the promise of the fully automated design of electromagnetic structures such as antennas, waveguides, metasurfaces and metamaterials; however, it can often yield designs that are incompatible with fabrication processes. In this work, we describe a multiphysics topological optimization framework that combines structural finite element analysis and electromagnetic finitedifference time-domain simulation to realize fabricable structures which meet specified electromagnetic design objectives. As a demonstration, the framework is applied towards the design of G-band low-profile leaky lens antennas suitable for future 6G communication applications. The 5λ0 radius, 2λ0 thick leaky lens antenna is compatible with stereolithography 3D printing and displays a realized gain of 23 dBi at 0.2 THz with a low sidelobe level of -20 dB. We foresee the proposed framework being applicable to a wide range of electromagnetic design problems intended for fabrication using additive manufacturing techniques.