I tried to help you, but I also can’t find it anywhere or I couldn’t find a fitting background which I could edit! 
Maybe you can sent a request on one of the Art Shops here!
Here are a few open Art Shops:
Olivia & Lily’s Unicorn Art Shop
Waves Art Shop
Cloudy Skys Art Shop! Open:cloud:
ℂ𝕝𝕠𝕦𝕕𝕪 𝔸𝕣𝕥 𝕊𝕙𝕠𝕡 {𝕆ℙ𝔼ℕ}
Lily’s art shop
Minimayday’s Art shop {OPEN} 
Bad Vibes Art Shop
Verve’s art shop 
(from Text overlays to Intro/Outro/Cover/Detail Ca
Time Trapped Art Shop
ROYAL ART SHOP 
{OPEN}
Enigma Art Shop OPEN
Or just type in the search bar: Art Shop.
I hope you can find what you are looking for 