Jay,
I thought that Ballard Brass made pinfire cartridges. They were purchased by Rocky Mountain Cartridges. I looked and didn't see any. However I did find they had 24 gauge pinfire cases in their inventory marked "no longer made." They would be the first person I would contact.
https://www.rockymountaincartridge.com/products.htm I found a supply of them in England
https://www.henrykrank.com/reloading...ire-cases.html Ross Seyfried wrote a great article about reloading pinfire cases decades ago in Guns and Ammo.
Harry