The D suspended fourth flat ninth chord is a 5-note chord consisting of the notes D, G, A, C and Eb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Db9sus.
Chords that are a superset of Db9sus. The chords include more notes but always D, G, A, C and Eb.
Chords that are a subset of Db9sus. These contain less notes but all of them are included in Db9sus.
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 Db9sus chord. Feel free to save or share the image as needed.