USB condom. And now I know. Where can I buy a trustable one of these?

Pretty easy to validate— you plug your device into a trusted computer first and it doesn't recognize it.

For Type A chargers they are readily available online and can be testing using the approach mikepurvis wrote in a comment parallel to this. Or you can make yourself a clunky one as it’s just two wires.

I have seen them called “data blocker” or “secure charging cable” but what you want is one that is a female-to-male device so you can attach it to charging cables not just bricks.

Type C is harder. I have one from the early days of Type C that doesn’t do PD so in the end it’s only useful for phones. I haven’t seen one that does Power Delivery.