"the countdown thing" is called the standard SMPTE countdown leader (usually used for film) and can be generated by Final Cut Pro and Adobe Premiere. Search for those terms and you'll find clips to download on the web and on YouTube.
If you want other types of countdowns, as you've discovered you can buy clips from various sources. Or composite your own using titles and a motion background. Another option is to use a timecode generator filter and run that clip in reverse.