As you now know, Heritage do them, about 6 quid for a bag of 50. The rubber bungs are too big, but Just Kampers list smaller ones for pre '73. (4 quid for 25). Don't know how much smaller and if they fit, 'cos my bus had not got a single one anywhere so I didn't use any. The clips are still a bloody tight fit into the metalwork, no way will they pop off! By the way, 50 clips don't go far if you got many trim panels to sort out.