Edit:
After a bit of a struggle getting it to do what I wanted, (and keeping with the Australia example, although modified):

This has a total of 53 points. Listing the coordinates will take too much space, so I won't.
Trying it on a accurate map of a medium sized island from the game (with more than average shoreline for the size and including a lake) gives a very tight fitting 116 points (< 8 pixels off at worst).
The accuracy can be easily changed though if that is too many or too few points.
