Gemlux,
Gemlux vent page has (2) but they will not fit, figured I would post part #'s just in case.
# 763:
Vent Louvered 4.5 X 8.125 In, 3.5 X 7.25 In Opening, Requires 4 # 6 Fasteners
# 765:
Vent Louvered 4.5 X 12.875 In, 3.5 X 12 In Opening, Requires 6 # 6 Fasteners
Both are stamped stainless steel