I've had a saved search on Ebay for "spiral skirt" for a long time. Besides the Birch Street, there isn't much out there.
Yes, I did list mine once, and it didn't sell!
I found these under "square dance", not even tagged with the keyword "spiral"!
Same background for both, so somebody's making them to sell...
I wonder if there's a pattern out there I don't know about, or they made up their own?