I'm assuming the OP wants to use semiconductor-grade photoresist because he expects it to be available for many years to come. Of course, this implies he will have to use TMAH (TetraMethylAmmoniumHydroxide)-based developer for his plates. Not so sure how easy this will be to acquire in small quantities.

An alternative process is photogravure, which uses a similar light-sensitive coated plate, but one which becomes water-soluble after exposure to UV light, making development much easier. I would assume the print-making industry will be around for a long time, and that there are enough artisans working in this medium (photogravure) to make the materials readily available for years to come. The process, you may be aware, produces a plate suitable for impression-printing in a press, using ink onto paper.

Properly printed to the right paper, photogravure images are wonderful to view and are very archival, and were in fact the first high-volume publication method for printing photographic images.

~Joe