So as title says I revived my beloved iPod, upgraded its storage and also modeled and printed some accessories for my iPod. I made a TPU case, a dock using the original cable and a storage box.
Everything is available for free on my printables:
https://www.printables.com/de/@Gorroth1007/models
Link to my first post (including whole storage upgrade process):
https://lemmy.world/post/3243217
Here are some additional pictures:
You should be able to put a 3000mAh battery in a 5th/6th/7th Generation iPod as long as you get an iFlash board and a Thick Backplate.
Edit: If you want the best place to buy iPod parts, buy them from Elite Obsolete on his website.
Thank you! Yes I know, but I wanted it to look like it was looking back then when I got it :)