AI Humanizer Recommendations?

The GPT I designed for myself through ChatGPT 4 does a great job writing business content for me (memos, letters, etc) as it’s programmed to understand my industry, company, and role. I’m just looking for a great AI humanizer/rewriting service (paid is fine) that retains the essence of my original GPT-drafted content, but just makes it undetectable as AI.

I’ve researched and tested several sites and the problem I’m running into is that they either make the writing much worse by messing up the context or using bizarre word/phrase choices, or they seem to incorporate minor grammatical mistakes on purpose to evade detection.

Can anyone recommend a truly stellar site that can rewrite with the quality of your original version, yet still evade the best AI detection tools? Cost is not a factor.