The easiest harness we have to put on and off quickly is the "choke free" harness. I know one YT vendor (mimimomo- Jenny) that does offer the choke free harness but you might want to contact her bc I notice on her site the drop down menu lists only the one size but mentions other sizes in the description.
Anyway, it is the most hassle-free harness out there and I've tried most all of them. They are a little more expensive than some of the other harnesses but are considerably less than the Susan Lanci ones. And, they are made of good quality leather, that gets softer with use.
toplinepet.com