Is genuine footage similar to the video I posted above actually exists and where I can find it.

Not really.

For one thing, gun camera footage was a highly ephemeral media. They were used to evaluate claims and a good many units did not keep these rolls of film for very long. Most aerial combats did not result in victories and there was little reason to preserve footage from indecisive combats. The net result is that a good chunk of the preserved footage was for pedagogical purposes. Some footage ended up preserved because it was a rare occasion where an attack went right and exposed weaknesses in enemy aircraft. Other preserved footage recorded mistakes made by pilots in combat. For example, look at this video, specifically footage starting at 1:29 and 2:03. In the first section of combat, a P-38 nearly strays into the line of sight of the attacking American fighter. The second section features an American attack on what is very likely a British Mosquito. So gun camera footage was preserved precisely because it showed pilots what not to do in combat.

The surviving gun camera rolls were incredibly short. WWII gun cameras typically triggered whenever the pilot fired his weapons. The ammunition load for WWII fighters on averaged only allowed for around thirty seconds of continuous fire. Training in all air arms emphasized the need for short, controlled bursts. This footage of taking on an Me-262 showcases some of the choppiness of the process at around the 0:48 mark where the attacking pilot holds fire while he closes the distance. As fighter guns became progressively larger as the conflict dragged on, only a few seconds of hits were needed to down an opposing aircraft.

There were handheld cameras available to pilots. This website has some preserved US pistol grip cameras. But fighter pilots would rarely use such cameras in aerial combat as they often had their hands busy! Aerial combat could be quite quick and surprise was crucial. There is an axiom that a majority of planes shot down never saw their attacker and while this is impossible to verify completely (dead men tell no tales after all), it meshes with fighter tactics. Another axiom common among a number of fighter pilots was that you wanted to avoid a turning dogfight at all costs. Such fights not only were often inconclusive, but they were disorientating and often led to the break-up in fighter formations. As Hub Zemke observed:

A major difficulty following a bounce or break in air fighting was re-forming a flight or section. This was normally achieved by radioed directions to form over a prominent landmark- if the ground was visible- or by a bearing reference to the bombers we were supporting. Even so, until pulling into a position where the letters on the next P-47 could be clearly seen, it was often a matter of luck if one was joining the correct slot.

And a fighter pilot without his wingmen was in a very vulnerable condition.

The haphazard method of preserving footage and the incredibly short nature of the material makes them insanely hard for aviation historians to gauge their provenance. A lot of filmmakers in the postwar period spliced together surviving footage with little regard to historical accuracy and this has found its way into various websites and documentaries. Thus is it not unheard of for aerial footage purporting to feature combat in the European theater to have a Japanese Zero wander in frame.

As for sources of combat footage, CriticalPast has some raw footage that is watermarked (although their website is rather buggy lately). Periscopefilm has stock footage for sale. Footage from youtube often has to be taken with a massive pinch of salt as not only is the footage often ripped from other sources, some of it comes from games like IL-2.