Magnetic Particle imaging (MPI) allows to measure and quantify background-free tracer distribution with a high temporal resolution. Anatomical structures are not displayed in MPI, rendering orientation within a sample error-prone and necessitating co-registration with other imaging modalities such as MRI. To support this challenge, defined external landmarks (fiducials) made from materials visible in each of the imaging modalities respectively were used in this work. Resulting signals can be aligned with the merged image containing both anatomical data and information about the tracer distribution. Defining the optimal fiducial placement is demanding and can drastically impact the 3D MPI-MRI image presentation. Here we present an adaptable 3D-printed fiducial system for preclinical co-registration of MRI and MPI data designed for easy visualisation. Clinical relevance- MPI is a promising imaging modality with many conceivable clinical applications. Simple and reliable co-registration with other imaging modalities will be crucial for a seamless transition into the clinic.