I'm not sure you can use << Get Script for what you are trying to do. And what you could/should do depends on your end goal. I'm pretty sure I'm missing something on why you couldn't use << Save Window Report but it could be one option
Names Default To Here(1);
report_win = New Window("Testwindow", << Type("Report"), Outline Box("tester", Text Box("Test")));
report_win << Save Window Report("$TEMP/test.jrp");
s1 = report_win << get script;
wait(0);
s2 = Parse(Load Text File("$TEMP/test.jrp"));
wait(0);
Delete File("$TEMP/test.jrp");
Show(s1, s2);
ob_script = Extract Expr(s2, Outline Box(WildList()));
s1 = V List Box(V List Box(OutlineBox(Text Box("Test"))));
s2 = New Window("Testwindow", Outline Box("tester", Text Box("Test")));
Outline Box("tester", Text Box("Test"))
-Jarmo