That's not just a standard C8 painted with an added dew shield. The tube is much longer plus the corrector's cell is moved forward on another piece of aluminum tubing. Not to mention what's that thing on the tube? In one still it looks like (pretending), he's using it to focus. I think it's either some kind of custom job or just a prop that they thought would look more impressive if it was made longer. Plus, check out the custom finder.
If it was done just for the movie, why would anybody bother doing anything more than painting one? Perhaps, to fit in with the overall gadgetry of James Bond movies?
I had a friend who did production design for movies. Before that he did model making for, among other things, James Bond movies. He had many stories about the incredible attention to detail that some directors (and production designers) have. When someone focuses a C8, it doesn't appear to do anything. In a movie, when a character is adjusting a piece of equipment, it should have a dramatic visual effect. While it would have been possible to get the effect with a refractor draw tube moving, that is a small effect, and it looks old-school. These are people who are used to camera lenses where the front element moves as its focused. Ergo, "Props department, fix that thing so the front moves in and out when he's focusing it!"
His model shop once spent a month building an ultra-detailed scale replica of Bond's car to be used in a scene where it jumps a drawbridge. When it was delivered, it got dropped and broken, so they rushed to assemble a plastic hobby kit overnight and do the best they could to paint it to match. It was only on screen for about ten frames anyway. Another thing I learned from him is that in outdoor winter shots, when there are icicles in the scene, they have to be replaced with glass because a shoot can span hours or days, and real icicles change shape, which would appear in cuts between takes.
So when it comes to movies doing crazy things, cutting up a C8 to make it visibly move when it's being focused is just another normal day in the props shop.