Always check the file includes diagram instructions, not just a crease pattern. Happy folding.

The Japanese Origami Academic Society publishes Tanteidan Magazine monthly. Several issues (especially #125, #137, and #149) feature Katsuta’s diagrams. You can purchase a digital membership to download these back issues as PDFs directly from their website (Origami House).

: Released more recently, this volume features 15 models such as the Siberian Flying Squirrel 2, Persian Cat, and Sparrow Gilad's Origami Page Where to Find Diagrams

While a direct, legal PDF download of his complete works is unlikely to exist, there are legitimate ways to access his diagrams: