Mockito: Mocking package private classes

I have the following simple DynamoDBDao which contains one method that queries an index and returns a map of results.

import com.amazonaws.services.dynamodbv2.document.*;

public class DynamoDBDao implements Dao{
    private Table table;
    private Index regionIndex;

    public DynamoDBDao(Table table) {
        this.table = table;
    }

    @PostConstruct
    void initialize(){
        this.regionIndex = table.getIndex(GSI_REGION_INDEX);
    }

    @Override
    public Map<String, Long> read(String region) {
        ItemCollection<QueryOutcome> items = regionIndex.query(ATTR_REGION, region);
        Map<String, Long> results = new HashMap<>();
        for (Item item : items) {
            String key = item.getString(PRIMARY_KEY);
            long value = item.getLong(ATTR_VALUE);
            results.put(key, value);
        }
        return results;
    }
}

I am trying to write a unit test which verifies that when the DynamoDB index returns an ItemCollection then the Dao returns the corresponding results map.

public class DynamoDBDaoTest {

    private String key1 = "key1";
    private String key2 = "key2";
    private String key3 = "key3";
    private Long value1 = 1l;
    private Long value2 = 2l;
    private Long value3 = 3l;

    @InjectMocks
    private DynamoDBDao dynamoDBDao;

    @Mock
    private Table table;

    @Mock
    private Index regionIndex;

    @Mock
    ItemCollection<QueryOutcome> items;

    @Mock
    Iterator iterator;

    @Mock 
    private Item item1;

    @Mock
    private Item item2;

    @Mock
    private Item item3;

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
        when(table.getIndex(DaoDynamo.GSI_REGION_INDEX)).thenReturn(regionIndex);
        dynamoDBDao.initialize();

        when(item1.getString(anyString())).thenReturn(key1);
        when(item1.getLong(anyString())).thenReturn(value1);
        when(item2.getString(anyString())).thenReturn(key2);
        when(item2.getLong(anyString())).thenReturn(value2);
        when(item3.getString(anyString())).thenReturn(key3);
        when(item3.getLong(anyString())).thenReturn(value3);
    }

    @Test
    public void shouldReturnResultsMapWhenQueryReturnsItemCollection(){

        when(regionIndex.query(anyString(), anyString())).thenReturn(items);
        when(items.iterator()).thenReturn(iterator);
        when(iterator.hasNext())
                .thenReturn(true)
                .thenReturn(true)
                .thenReturn(true)
                .thenReturn(false);
        when(iterator.next())
                .thenReturn(item1)
                .thenReturn(item2)
                .thenReturn(item3);

        Map<String, Long> results = soaDynamoDbDao.readAll("region");

        assertThat(results.size(), is(3));
        assertThat(results.get(key1), is(value1));
        assertThat(results.get(key2), is(value2));
        assertThat(results.get(key3), is(value3));
    }
}

My problem is that items.iterator() does not actually return Iterator it returns an IteratorSupport which is a package private class in the DynamoDB document API. This means that I cannot actually mock it as I did above and so I cannot complete the rest of my test.

What can I do in this case? How do I unit test my DAO correctly given this awful package private class in the DynamoDB document API?