I don't have one in front of me, but try the afloat shopping guide. Last time I looked, it had the NSN's for the individual parts of the bullseye kits.
While on war cutter MUNRO we ordered individual blue and red letters before CART from 3M. The numbers you need are on the disc that comes from 3M. If you dont have the disc I suggets getting in touch with DC2 Green or DC2 Ledford and they should be able to help.