There's several of these on shadertoy

https://www.shadertoy.com/results?query=crt

I made a Pico-8 post processing script using a few

https://greggman.github.io/pico-8-post-processing/nano-villa...

also an article on starting one on WebGPU here

https://webgpufundamentals.org/webgpu/lessons/webgpu-post-pr...