Get free and paid resources for VJ loops:
1. Finding video sources (overlays) and free materials on YouTube:

If you search YouTube for video effect source? or green screen footage source, you can find a lot of good stuff by typing in words like 'green screen'.
I think the words footage and overlay are often used.

For comprehensive words, I search for 'overlay' or 'effect' like this.
When I need a video source, I seem to search for a word that suits the situation at the time.

(the word you want to search for) + gb / green screen / source / video source, and so on, and then I go back and forth and try them all.

Or I just use Overlay and hit it as it is.
vj loop, fire, vhs, film, background overlay, etc.
Or you can search for the word elements pack and get it.
It is also a way to find it in Japanese by typing the words 図形素材 フリー素材
I think it's best to search in the US and Japan.

When searching on YouTube
I use playlists rather than channels

You can probably just go through the channels in the playlist.

I've gotten a couple 4k's from VJing on YouTube.
It's not just a few. It's like a whole playlist.
There's like 300 of them.

Example:
https://www.youtube.com/results?search_query=VJ&sp=EgIQAw%253D%253D
https://www.youtube.com/results?search_query=%E7%84%A1%E6%96%99%E7%B4%A0%E6%9D%90&sp=EgIQAw%253D%253D

2. Get free and paid resources for VJ loops: https://docs.google.com/spreadsheets/u/0/d/1VKPjlPoO0wiIhGEnL32reVAMNtcPKZ205viEvGNhddQ/htmlview
https://docs.google.com/spreadsheets/d/1Dmr-6crDQvSOI68kHEt0w6h5r9xsZGMx5y9LnZ9M5Uk/edit?usp=sharing
https://www.jasonfletcher.info/vjloops/vj-content-creators.html

Envato Elements, MotionArray has a large collection and paid, but just sign up for a month and you have access to everything, https://gumroad.com/?query=VJ
https://gumroad.com/?query=VJ+LOOPS
gumroad has many great creators

https://www.youtube.com/watch?v=LvUJ2ZzOkjM

https://archive.org/search?query=VJ+loops
https://www.reddit.com/r/VJloops/
https://www.reddit.com/r/visuals/
https://pixabay.com/videos/search/vj%20loop/
https://www.pexels.com/en-us/search/videos/vj%20loop/
https://www.freepik.com/search?format=search&last_filter=selection&last_value=1&query=vj+loop&selection=1&type=video
https://www.videvo.net/search/?q=vj+loop&mode=video
https://www.avloops.com/free-loops

Make your own : https://www.resolume.com/ resolume arena, https://derivative.ca/ Touchdesigner

Tutorials : https://www.reddit.com/r/vjing/comments/13tdwll/i_just_released_another_huge_pack_of_50_original/ https://www.reddit.com/r/vjing/comments/18g3jty/tips_on_creating_vj_content/
https://www.youtube.com/results?search_query=resolume+arena+tutorial
https://www.youtube.com/results?search_query=Touchdesigner+tutorial
https://www.reddit.com/r/vjing/