If you know of any, let me know. The problem is that any harness you buy will get more loose as it is warn, and panicked dogs can get out of a harness the same

If you know of any, let me know. The problem is that any harness you buy will get more loose as it is warn, and panicked dogs can get out of a harness the same way you can get out of a t-shirt: line your head and arms up along the same axis and back up. A harness is only really effective if the dog is moving forward and away from you, not if they are backing away from you in a desperate panic.