You can build a wrapper function like this:
function get_something(name in varchar2,
ignore_notfound in varchar2) return varchar2
is
begin
return get_something (name, (upper(ignore_notfound) = 'TRUE') );
end;
then call:
select get_something('NAME', 'TRUE') from dual;
It's up to you what the valid values of ignore_notfound are in your version, I have assumed 'TRUE' means TRUE and anything else means FALSE.