Fighting 15s now have stock of the Extra Impetus 3 rulebook.
From their website:
Fighting 15s has taken delivery of Extra Impetus 3, the third supplement for Lorenzo Sartori’s ancients and medievals wargames rules. This full-colour softback comprises 44 pages plus covers and includes 46 army lists that cover four periods: Italy in the 15th century, Europe in the 15th century, the Wars of the Roses, and the Ottoman Empire.
Extra Impetus 3 costs £14.50.
The main rules are now back in stock, along with the first two supplements. All are available in the Fighting 15s shop.