bandpass fillter design in simulink

A signal, which is a output of a simulink submodel with harmonic frequency at 20-30Hz, has great influence on system control performance.

You can consider this signal as a analog signal, is there any method can be applied to extract these harmonics without phase shift?

I thought that bandpass filter might be a good choice, but i have no idea in digital filter and how to use the @simlink submodel "bandpass filter", as shown in the following figure.

So i am wonder is there any other substitute options to bulid a bandpass filter with narrow bandwidth and fast roll-off, for example, use transfer function?Can anyone give me some advice?