DFM,
I have the following OB posted over on TheVirtualArmchairgeneral.com:
Parade State and Order of Battle, Sikh Supplementary Force, 1st Afghan War, 1839
Also, go to Google Books and Archive.org and do a search for the following key words:
Claude Wade Khyber (<--various spellings)
You should get at least two books, one by Wade another by Ali (methinks).
There is also an article in the United Service Magazine (again avail from Google Books for FREE) titled:
"Forcing of the Khyber Pass under Lt. Col. C.M. Wade
(United Services Magazine 1842, Part 2)
You should be able to download a pretty decent amount of information for free from these two sources alone
let alone a regular Google/Wikipedia search.
Hope that helps
Andrew