Please refer to this topic. It has a sub-discussion of shoulder harness attachment with a lead on the shoulder harness cross bar. This is only the most recent topic where this has been discussed.
Rear wind shield
Search can be your friend. If you go to advanced search and search for "shoulder harness" in titles only there are lots of topics on the subject. If you search for "shoulder harness" in the body of the topic there are too many to list but many have additional useful information. As with most questions about Cobras, almost every question that can be asked has been asked so many times that the answers you're getting have been given many times as well
. "There are no stupid questions, only old questions..."
The source referenced is finishline. They have a rather bad reputation for delivery of recent so perhaps someone can post a better source. I can't remember the name of Drew Serb's store. Also I'd bet that Hillbank and/or Denbeste has them. Also Shell Valley in Nebraska also has a pretty comprehensive parts supply. Kirkham might be a source too.