Real smoked bacon is the way to go, though you won't find it in an American supermarket (just fake smoked bacon), just some ethnic European stores at best. Sadly all the Polish meat shops have long since closed around here..
Didn't take long to find:
https://vanderosefarms.com/product/americas-best-uncured-bac...
Vande Rose Farms states: ALL NATURAL INGREDIENTS
but — among them is "cultured celery powder" which indeed "contains nitrites as well."
It would appear Vande Rose Farms is hiding behind the USDA definition of uncured — as do other makers — to seem more "natural."
They also offer a Dry Cured version: https://vanderosefarms.com/product/americas-best-cured-bacon...
I am reminded of a dialogue I had with an area representative for Boars Head Meats whom I met while he was arranging his display in a Kroger store.
We got to talking about cured vs. uncured meats and I decided to really get to the bottom of it (this was maybe 10 years ago).
After significant effort I discovered that "Uncured" products actually contain MORE nitrites and nitrates than "Cured" because it is impossible to accurately measure nitrite/nitrate levels in the celery powder extracts used in "Uncured" meats so manufacturers routinely add much more than they would otherwise need to so as to be able to always pass FDA tests for bacteria etc. growth. required for certification.
I sent my findings to the Boars Head rep and he was surprised and agreed that I was correct.
Also, here's another result from walmart: https://www.walmart.com/ip/Great-Value-Sliced-Hickory-Smoked...