The G suspended fourth flat ninth chord is a 5-note chord consisting of the notes G, C, D, F and Ab.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Gb9sus.
Chords that are a superset of Gb9sus. The chords include more notes but always G, C, D, F and Ab.
Chords that are a subset of Gb9sus. These contain less notes but all of them are included in Gb9sus.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the Gb9sus chord. Feel free to save or share the image as needed.