Ask HN: How do I find an agent?

I want an agent. I'm a mid career software engineer and I feel like I could be better building a personal brand and finding higher compensation positions. I can do all this myself of course and have, but I'd really like to hire someone whose mission is to advance my career. Find very specific positions, reach out to companies on my behalf, suggest ways I should be advertising myself, do a bit of that advertising on my behalf.

"That's a recruiter/headhunter" - Sure! But specifically I want to pay them and not have them shop me out to companies who might also pay them. I'm fine paying a retainer on top of the standard salary percentage for a new gig.

Have you done this? How did you make it work?