Hi!

Welcome to YT. You're correct. You never want to attach a leash to the collar on a yorkie.
There are lots of great anti-pull harnesses out there.
Just google anti-pull harness and you will see many examples. This is just one example:
Anti-Pull Mesh Harness: Yuppie Puppy Pet Products
I forgot to add that the reason it is not safe to use a collar to walk a yorkie is because it can harm their trachea.