The alternatives are:
1-You make your own, for monochrome or tricolor work.
2-You use Ultrastable color tissues for 4-color work, but this
requires the use of negs screened on a high-end color scanner.
BTW, The _Maine Photographic Workshops_ has workshops teaching the use
of Ultrastable materials and how to have color seps made, etc., this
summer. I am not involved with these workshops myself this season
(like I used to)
Luis Nadeau