There are a variety of cheap 1080p options

https://www.amazon.com/TreasLin-Recorder-One-Click-Recording-Compatible/dp/B08LPSG8CY

https://www.amazon.com/ClonerAlliance-Recorder-Playback-Converter-Required/dp/B012T1D0IG

Never used one myself.

I think for your application it will be key that it accepts a 4k signal even if only recording 1080p