Here is another thought.
We use a harness for Ella when we go outside but what she wears around her neck all the time is a DAP collar. I assume you are familiar with them, but they are disposable rubber strip collars that release a relaxing phermone. They last a month. Maybe either the rubber or the phermone will help chewing on the collar.
As far as a tag that cannot be chewed, I hightly recommend the collar-tag from boomerangtags.com. They are made of sturdy steel that slips onto the collar itself and do not hand down at all. Solved our problem tag chewer.