if you cant create types (you can't just use sql*plus to create on as a one off?), but you're OK with COLLECT, then use a built-in array. There's several knocking around in the RDBMS. run this query:
select owner, type_name, coll_type, elem_type_name, upper_bound, length
from all_coll_types
where elem_type_name = 'VARCHAR2';
e.g. on my db, I can use sys.DBMSOUTPUT_LINESARRAY
which is a varray of considerable size.
select department,
cast(collect(name) as sys.DBMSOUTPUT_LINESARRAY)
from emp
group by department;