Sweetwater was back in-stock on a few of them, as of a couple weeks ago anyways.
You might try reverb since there are lots of smaller dealers on there too. (recently snagged a Nazgul trembucker from Pilgram's Projects in Michigan)
edit;
Sorry it's "Pilgrim's Projects" from Hastings Michigan on Reverb.
Obviously Banjomikez is another place to check, he's usually my first option when wanting something shop-custom or something that is out-of-stock at the big stores.