Dielectric wire media are modelled both numerically using CST Microwave studio and analytically as media with spatially dispersion. In the latter case this leads to a differential equation that can be solved in terms of Mathieu functions. A periodic variation in the radii of the wires is considered as a method for shaping the propagating mode shape. A profile is proposed which gives a flatter shaped mode. Such a mode would increase the acceleration of particles in a particle accelerator.