I have never seen any reference to cable clips in the spare parts books, but when I purchased my Dragonfly (in pieces, from the original owner), there were some used soft metal cable ties in the boxes of bits. Years later, when we collected Graeme Brown's postwar spares for the Club's spares scheme, there was a bundle of these cable ties in the drawer full of electrical bits - so I guess they were the correct ones for the Dragonfly. They were in the form of a headed metal strip with a narrow slot across the head. In use, the strip is just bent around the frame tube and harness, the tail poked through the slot and bent back on itself.
Hope this helps,
Regards,
Eddie.