We only sell a small curated selection of items that experience has shown to work well. Here are some suppliers whose products we also use and recommend:
Precision Digital Negatives
Mark Nelson has created an easy-to-use digital negative (and positive!) system that alleviates much of the pain involved in creating alternative process prints that look just like the image on your computer monitor.
He also spent much time and effort creating a selection of aquatint screens used in the photogravure process. Unique among providers of these aquatint screens, he can provide coarse, medium and fine-grained screens in a variety of sizes. We like them so much that we include his 10"x12" medium screen in our polymer photogravure starter kit!
Here is a link to his online store: Precision Digital Negatives
Richard Boutwell is another digital guru that has created a family of applications that allow printmakers who use the QuadToneRIP application to create linearized printing profiles for making prints, positives and negatives. He has greatly simplified the technical know-how that was previously needed to use QuadToneRIP with the Epson inkjet family of printers.
Here is a link to his online store: QuadToneProfiler