Parasolid CAD formats, including X_T and X_D formats, are well-supported in many CAD programs or dedicated conversion programs and as such it should not be hard to find a software capable of x_t to igs conversion. You can even find online converters that offer ways to convert x_t to igs directly through your web browser.
Open X_T file Open IGS fileA CAD conversion software
A CAD converter with huge format support
A CAD visualizaton, analyzation and translating system
A 3D geometric modeling component software
A 3D CAD translation software
A suite of CAD applications
A dedicated CAD converter