I work in the UK head office of a top-5 FTSE100 company. A few thousand people on our site.
The CEO wears jeans, when he can. I wear jeans, t-shirt and trainers pretty much every day. People take the mick if I’m in a shirt. Most of the rest of the board wear jeans too, when they aren’t entertaining visitors from more dressed-up companies. I’m in the same building/same floor as most of them.
I’ve been known to wander around the office at the start/end of the day in full euro-roadie lycra too.
Our dress code is “wear what’s appropriate”, so people out visiting customers or hosting them on site will tend to dress how the customer dresses – mainly in suits.
You just need to find the right company.