One of the options for obtaining a sugar glider as a pet is rescuing one or obtaining a sugar glider from a rescue. Or adoption through somebody who can no longer keep it and would like to re-home it.
There are a number of organizations that will take in unwanted or un-cared for sugar gliders. Rehabilitate those and re-home them. And that's going to be contingent on the state in where you live whether there is a sugar glider rescue in your area.
There are a number of people who would preferably not want to get a sugar glider from a pet store for personal reasons. Or they may not want to seek out a breeder or pay for what a breeder may require for obtaining a sugar glider. And they may want to seek out alternate sources.
Sugar glider rescues certainly serve a need. They're an excellent option for people who may want to get additional sugar gliders to add to their current. Or they may have lost a sugar glider for some reason and want to get a new one to keep company an existing sugar glider.
So, check with your veterinarian. Check with local humane societies and local animal rescue groups to see if you can find any information on someone who would be likely to have and be willing to readopt any rescued sugar gliders.