chemically inert molecule with piezoelectric properties
The ur-piezoelectric crystal is quartz. Being composed of $\ce{SiO2}$, it more or less epitomizes chemical/biological inertness. It has the additional advantage of being comparatively cheap and common. There are a number of other natural minerals which are piezoelectric (e.g., various perovskites). Most of those minerals are, as far as I know, relatively unreactive and non-toxic. Naturally, if toxicity is a concern, avoid the common lead-based compounds.

I've seen mention of materials that exhibit both ferrimagnetic and piezoelectric properties. If ferrimagnetism is acceptable to you instead of paramagentism, then you may wish to consider that as an avenue for research. If you need paramagnetic materials specifically, then it's probably not worth your time (unless your project is compatible with subjecting those materials to their respective Curie temperatures).