Did you check the datasheet for that connector, and compare it to your cable diameter? It says it comes with seals to fit cables from 3.5 to 7 mm.
http://www.assmann.us/specs/A-HDx15-HOOD-WP.pdf
That is a waterproof industrial connector, and is EXTREME overkill for your application. It may have issues mating with a standard VGA connector on a computer (going to be physically bulky so clearance becomes an issue). And they cost $11 each!
You need to MEASURE your cable diameter, and RESEARCH the various connector hoods/backshells that are available. READ datasheets, and SELECT one that will fit YOUR application.
None of this is rocket science. But it takes a bit of effort to dig through datasheets and find a part that will work for you. Nobody else is going to do your research for you...