There is. It's slow, and tedious, and expensive, but you can do it.
Fly North until you're just about to leave the bubble. Find a starport out there on the frontier with a shipyard, buy a Sidewinder there, and park it.
Repeat for South, East, West, Up and Down. Distance-wise, it's about 200 LY in North, South, East and West directions, about 250 LY Up, and about 300 LY Down.
You now have a rough approximation of the extent of the Bubble which you can see on the galaxy map. Feel free to add more "surface" to it by visiting more frontier shipyards and buying more Sidewinders.
Once you've done this, and for a comparison, switch your map over to the Powerplay overlay. You'll notice how only a relatively small fraction of Human space is Powerplay controlled, in the centre of the Bubble. The Frontier regions aren't profitable enough for the Powerplayers to expand into.
For a final touch to your map, fly out to the inhabited Outback systems way out in deep space, like Sothis, Quince, Fehu and Canopus, and buy Sidewinders there, too.
Now zoom way, way out as far as it will let you zoom... and you can realise just how tiny is the slice of the galaxy which humans actually own.