Why don't you just try to register a homemade firearm?
$10 from Home Depot
Needs to be a handgun, Needs to be registered with HPD,
Also, In Hawaii you cant make a gun without a permit, Doing so is a violation of HRS 134-2
No person shall acquire the ownership of a firearm, whether usable or unusable, serviceable or unserviceable, modern or antique, registered under prior law or by a prior owner
or unregistered, either by purchase, gift, inheritance, bequest,
or in any other manner, whether procured in the State or imported by mail, express, freight, or otherwise, until the person has first procured from the chief of police of the county of the person's place of business