Here's a good thread over at holoforum.org about sensitizing dyes... http://holoforum.org/forum/viewtopic.php?f=9&t=494

Some of the links to various dye companies seem like good bets for obtaining these dyes.

http://www51.honeywell.com/sm/specia...zers.html?c=23
http://www.corchim.ru/catalog/Phot-sen_PH.html (google translated, here)
http://www.organica.de/en/download/1...cification.pdf (it's interesting; this dye is sold at HW Sands, but as a functional laser dye, not necessarily advertised as a red sensitizer as it is at this website.)