I used aluminum flashing to shim mine. You can buy a small roll at home improvement stores (roofing/siding materials). Using tin snips, cut a rectangle that's long enough to reach past the wedge on the end of the stem. Wearing gloves, give it a fairly cylindrical shape by pressing it around a broomstick or tool handle. If it's still too loose, fine-tune by adding similar pieces of beer can or soda can.