The 30 to 31 NWF clasp to be attached to the Indian General Service Medal for the red shirt & Afridi rebelion was awarded to the men of these British units.
15th/19th The King's Royal Hussars
1st-12th Armoured Car Companies,
2nd Battalion,The Border Regiment
2nd Battalion,The Royal Sussex Regiment
2nd Battalion,The South Lancashire Regiment
2nd Battalion,The Essex Regiment
2nd Battalion,The King's Own Yorkshire Light Infantry
1st Battalion,The King's Shropshire Light Infantry
2nd Battalion,The Durham Light Infantry
2nd Battalion,Seaforth Highlanders
Probaly many British Indian units as well. I havent got access to a list of them for that action.
It was also a Garrison town with other units residing there but not all units in the Garrisons saw action or therfore got clasps.
A letter to each Regimental museam curator , should pull up a few sellers amongst them.

They will all say any sellers they find could be your man! i used to get excited at first. Then I learnt more.
Sorry Lew I cant say it easy, Ive traced so many names till I reach the "well it could be one of these 3 or 4 guys stage."
But luck might win out!
Spiral