These are called ladder jacks. They are available at most hardware stores that sell ladders here. In my region you’re still allowed to use them if you set up guardrails or are tied off. I was working on my own house in this video so there are no governing safety regulations for working in your own home. They are definitely VERY handy for small jobs like this where setting up pump jacks aren’t really worth it and where you can’t access the location via a man lift. With anything, there are risks -

This homemade ladder jack I built is an oldschool carpentry tool. It's been around for along time, but unfortunately it's been banned in some countries. In my opinion it's an awesome tool that makes working on a ladder easier & safer. It can also be used for scaffolding which is much easier in certain situations #ladderjack #ladder #ladderwork #diytools #diytutorial #diyproject #homerenos #homemadetools #homemaintenance #renotools #renotip #carpentrytools #carpentrywork #carpentryskills #scaffol

Qualcraft Ladder Hook with Wheel