Cheap replacement for Flatfield light foil Flatfield generator Flatfieldbox

If the flat-field filters specifically designed and manufactured for telescopes are too expensive, there are several cheaper options.

Either a video light, an old iPad or similar device, tracing panels, etc.

For example, see Amazon:

https://www.amazon.de/gp/product/B0755D5CLS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1