I fear there is no genuine way of getting links from gov sites
In the USA, it's tough to get links from the Federal government but we've had luck getting them from State sites.
First step is to register your business with the State you have your business license with, you can't be linked to unless you are a registered vendor with the State.
Go through the State site carefully, take note of how they link, where they're linking to and what their rules are.
Most businesses fail at link building because they don't read the guidelines/rules of the sites they're submitting to.