As Dax posted earlier, I also received the 2013-2014 availability listing for Treehaven Evergreen Nursery. Don has Pinus szemaoensis listed among his other offerings. His availability sheet notes it is hardy to USDA z5 and has 7"/17.75cm long needles. Forestfarm has the same information listed.
The only other information I could find suggests that P. szemaoensis is a synonym for Pinus kesiya var. lanbianensis, which I believe is a tropical pine species and not hardy to USDA z5!

If anyone has more info on this species and can clear up my confusion, please let me know! I would like to know if it is worth trying for me or a waste of time (i.e. nowhere near cold hardy enough). Thanks!