Sorry I have come late to this thread. The bag is known as "Satchell, Grenade accessories" and is for the L2 HE grenade rather than for smoke grenades. The accessories in this case are the projection adapter (Adapter, Grenade, Projector, L1A1) and the cartridges (Cartridges, SA, 7.62mm, Rifle Grenade, L1A2) [1967 nomenclature].
The satchell was "designed to provide a convenient means by which a soldier may carry the adapters and cartridges without affecting his personal eficiency". Five satchells were part of the contents of the ammunition container (L1A1) (steel) holding 25 adapters each fitted with a cartridge in a plastic holder.