They're fairly rare birds to be honest but try setting up an eBay alert and signing up with either watchrecon or watchpatrol. Or you may well be lucky and of our lovely members may be willing to part with theirs
I'm picking mine back up from my watchmaker tomorrow. He's just fitted a NOS bezel for me
One other place you might add to your hunting list is watchesulike. It's out of France. He will often get NOS dials and parts -- and he usually has a bunch in stock. I've had a mixed experience -- though the items I've purchased from him are genuine, his customer-service/fulfillment isn't always the best. Sometimes it takes a while to sort out delivery. He can be responsive and helpful though.