Just use galactic center-centered coordinate system in higher-base numbers.
Instead of hexadecimal, you can use base-32 and make the numbers 2 times shorter (and 3 times shorter than decimal with the same accuracy)
You can even go base-36 (10 digits and 26 English/Latin letters) and your coordinates will look like:DCA4/PGS0 (angle and distance from the center, accurate to well within light-year)
This is enough not to get lost in the sparsely-packed habitable regions.
Regions with a dense population of high-mass, bright, short-lived stars and their remnants (neutron stars and black holes) may be scientifically interesting, but neither habitable nor easily navigable (strong EM radiation all over the spectrum, convoluted gravity and fewer planets). Whoever goes there will add a character or two for accuracy and a third number.
