Of course the third source to find inspiration is through..
And not just any music. Certainly not those music with lyrics lol. The best way to get inspiration from music is to listen to anything instrumental. Classic and World music will be good choices as well.
Listen to the notes, the tempo, the emotions that flow, and learn the story and history of each song and also the artist.
The longer and the more diverse your playlist, the more inspiration that you could get.
If this is your first time on exploring music, just take your time. Listen as many as possible, even the ones that are not your cup of tea. You'll learn something, somehow.
Music with lyrics will only be useful once you could listen without really listening. This one might seems not making sense lol, but it does happen that way.
When you get used to it, music will only be a backsound that manage your rythm and energy level. You won't even really listen to it, won't be annoyed by it, it will just flow and pass, but you surely feel something is missing when you don't have any music with you lol.
For you who are not really into classical and all, you might try to find modern instrumental such as Yiruma, The Piano Guys, etc.
I was listening to Berlin by The Piano Guys when I wrote this, in case you are wondering. I need the beat and the flow to make sure my fingers pace up with the words came out from my mind. Lol.
Ps: Photos on this post don't belong to me, and are the respected works of each of the owners.