Data blocker device for public usb charging my iPhone?

Do not let yourself get excessively frightened by posts on social media, even if they did original with the FBI. See this article for a little much needed common-sense:

https://slate.com/technology/2023/04/free-public-phone-chargers-fbi-warning-bad-actors-threat-bogus-debunked.html

Hello,

I am not aware of any that exist. Public USB charging has always been risky.

A much better approach is to carry your charging cube and plug it into an electrical outlet. That should be safe.

Good luck.