Here's a link to the thread in the breeder's forum of this site and the discussion we had about CT. It has most of my sources listed there and a pretty good summary of what we know about CT.
http://www.yorkietalk.com/forums/showthread.php?t=18164
As for harnesses, thank goodness you don't use a collar on a ST positive dog. That would be nasty. I'll share what harness I use with you, but please remember that there's no one brand tailored for your dog, you will need to ensure a good fit and make sure that the thoratic trachea is clear from pressure before taking this out and about.
I use a VestHarness. It's quite comfortable and Chewy doesn't mind wearing it full-time! It also is super easy to put on and take off since it has TWO quick latches on the top. No stepping in, and no wrangling a loop over one leg kinda stuff. It's also really durable and is built so that you can run a seat-belt loop through it and buckle your buddy in for a car ride.
Here's a pic of Chewy in his VestHarness.