Do it your self.
Open a new sequence and put a 3/4 frames (3 in PAL land) piece of Bars&Tone.
Copy and paste it every half second, so leave 9 space frames between clip and clip.
When you have few of them in the time-line, select all of them and copy and paste as many times as you need.
In NTSC I guess is the same, a bip every half second more or less.