They're expensive and the lead times can be long but Nicks Handmade Boots is known for having some of the most heavy duty, durable boots you can buy and they go up to FF. I'm not sure but they may even go up to FFFF on custom orders (long leads). My neighbor just bought a pair of Ready-To-Ship 10.5FF Urban Drifters last week and received them within about 4-5 bus days. Good luck.