Much like Dave, my source for those is Exotic Blanks. I try to stock up when they sell them because they typically sell pretty quickly. I've not looked around to see if anyone else sells them. I occasionally see things advertised on social media but never follow up on them because I've no idea of who the seller is and if they can make a decent blank. The blanks from Exotic Blanks turn so well that I haven't bothered to explore anyone else.
Dave - they had them at the 2025 MPG too, glad you're feeling better, we missed you this year.