You should get in touch with people from Kew or Hortus Botanicus Leiden. They have collections dating back to the very beginning of the orchid craze and are cornerstones of orchid history.
Bernard Lagrelle from France is a very, very talented Phal grower who has spent years gathering all kinds of historical documents, it might be worth asking him as well.
Finally, I would recommend checking out the works of Sweet, Reichenbach, Veitch (obviously you've done that one), Rolfe, and Chistenson.
Definitely read the reports Micholitz wrote