This is not going to be easy, hope you mean something for a permanent installation.
My idea would be some kind of bushing that lets the main wire pass through to give you enough isolation. Then you put a toroid around that bushing, and cut a slot in the toroid into which you place your hall sensor. AKA this https://www.digikey.com/en/articles/techzone/2012/sep/~/media/Images/Article Library/TechZone Articles/2012/September/The Basics of Current Sensors/article-2012august-the-basics-of-current-sensors-fig1.jpg but packed with isolation between the ferrite and the wire.
You might be able to make some sleeve from say hdpe or teflon or something and put it inside some ready made sensor. Dont forget clearance on the sides as well.
Looking at some numbers from over the net a wall thickness of 10mm should be more than enough, but the clearance on the sides will be somewhere around 100-200mm. You could pot the sensor to come over the clearance issue.