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
Does the camcorder still work? If it does then that would be the best way to play the tapes. You can capture the video with a whole slew of different products, one that would probably work good for you (since you're looking for upscaling) is a cloner alliance box pro.https://www.amazon.com/dp/B012T1D0IG