About an hour from Figtree (according to Google Maps) would get you to say Kangaroo Valley - I don't have anywhere specific in mind there though.
Seven Mile Beach might be worth considering.
I'd suggest you would want to be going away from the Sydney glow, so I'd suggest south or southwest.
If you can stretch your travel time to say 2.5 hours, Kioloa on the south coast has some very dark skies according to the light pollution maps.
Al.