My Parker is a little munchkin. I have had success with:
* Wonder Walker - Size Toy
These are sold in the Pacific Northwest in stores, but you can order online. The benefits are that there's a hook on the back for free roaming, or on the front for guidance and to train against pulling. It was fine, but Parker hated it going over his head. He was more of a polite walker when it was clipped in the front and it was nice to clip the extended leash on his back and let him RUN!!!
* Easy Walk - Size Petite/Small (not petite or small, but the actual size is Petite/Small)
These don't go over the head. They are adjustable in many places so an impatient dog needs to be held still to get the fit right. Like the Wonder Walker, there's a front leash attachment for a guided walk, but no attachment on the back. The hook on the front is in a different place and somehow further improved our walks, even better than the Wonder Walker.
I'm big on pups with manners and switched a friend's puppy CockerPoo to front-looped harness (properly fitted) when he stayed with for a couple weeks. With mild voice correction he became a better walker in two walks.
About Parker: 9.5 lbs, slim body, usually has a weird fit because he's in the Long & Lean category. The shenanigans in finding coats and harnesses made me crazy. If I can help you avoid it, I'd be happy to.