Blick Art Materials primarily stocks Akua clear PETG plates, which are ideal for use with photopolymer films and monotypes. Prices range from roughly $8 for a 3-pack to $91 for large bulk sets.
If you do not have an exposure unit, these "trade shops" will take your digital file and send you a processed plate ready for the press. Boxcar Press Letterpress Shop Print shop ClosedSyracuse, NY where to buy photopolymer plates
A specialist in fine art printmaking, Takach Press stocks Toyobo steel-backed plates. They offer varying sizes, from small 5.75" x 8.25" sheets starting at $10 to large 23.375" x 33" plates for $134 . Blick Art Materials primarily stocks Akua clear PETG
A reliable Canadian source that processes KF95 plates. They charge roughly with a minimum order of 35 square inches. Screen printing supply store ClosedL'Hospitalet de Llobregat, Spain Boxcar Press Letterpress Shop Print shop ClosedSyracuse, NY