We got ours by politely asking, and implying we'd pursue further testing.
We were surprised that extended norms were neither used nor mentioned by our tester, who is known locally as an expert on gifted children.
Someone who no longer frequents this board calculated them for me and DD8's FSIQ did not increase, but her GAI increased 5 points, which is quite a leap as far as IQ tests go, and if you are advocating it can be huge.
One interesting aspect to our raw scores was a Test Age Equiv. column, which showed DD (at age 7) scoring the equivalent of age >16:10 in two subtests. Far more than the IQ score, that way of looking at it helped deepen my respect for how profound asynchrony must be for DD in school and life.