Depends how hard you wish to shop.Have gotten some from Regal, and Florin Tractor is always worth checking.
Do they sell bulk material? I'm looking for a place to buy the raw material rather than pre-cut/drilled pieces. If I can find a source of it reasonable I may start doing some custom friction lining work for folks too.
Both have delete in inventory from dealers wanting to move old inventory so they may have the cut and drilled at a price that cannot be matched. Regal may have moved on to only selling new after market but started by selling old stock parts.
I was i Thailand recently and found a few shops there that sold brake material in bulk and in all different sizes, i have got a card for them somewhere at home, they will probably sent to you but you have to speak Thai as this helps greatly.
Regards