Mocha is 3lbs and has had several different types of harnesses. The one I like the most is the Buddy Belt
Welcome to BUDDY BELT (A Division of Class Art Productions Inc.). He's been able to get out of, or crossed/mixed up in other types of harnesses. He also has a Puppia vest harness, which is another one that he can't get out of or get caught up/tangled in, but since it covers a lot more area on his body, his hair always gets matted and needs to be thoroughly brushed afterwards.
I would highly recommended the Buddy Belt, or the Choke Free Harness like the one posted above by Wend. They're both a similar design, just different styles/looks. I bought the Buddy Belt before noticing the Choke Free Harness, but I think I'll end up getting one of those because I like the look of it a little better. But for now, the Buddy Belt will do
Oh, I also like that it feels more sturdy/secure and doesn't slide around like other step-in harnesses do!