Just another idea,
You could try Reloading.org.uk, they may have something in stock or... I was after an 8g flat bottomed jag and a breach scraper for the blunderbuss and they made me them from my own dimensions. Very quick and very good workmanship... but not cheap around £40 each with postage ? Not much choice, 8g cleaning gear like that is as hard to find as the proverbial.