Clips can be good for keeping one bit off another and prevent chaffing, secure the route, reduce vibration, other stuff, letting things wave in the wind isn't always best but often perhaps one missing fixing doesn't matter, all depends. Concours of course is a different matter, can get very anal very quickly. Somewhere there will be a clip sold that will do the job, you might have to buy a packet of a dozen, or 100 or 500 but if from China they'll be so cheap it won't matter about quantity and you have replacement spares (which you might need). If you go to garage or car supplier websites you'll find fixings for the various manufacturers of cars and generally just takes so longer to match up all the options offered against what you need. Only a few years ago you could still get a paper printed colour catalogue posted to you, possibly still can, I don't know. I bet there still might be someone or somewhere in the Czech Republic that has stock of the original but it's a matter of you finding them. If any army used that part then stocks of them can appear decades later with specialists, not sure they'd bother with a plastic clip though. A mate got an out of contract (30+ years) NOS engine, been in his 1960s car for a few years now., the engine had a long production life, British of course, tuned it nicely goes very well.