Where can I find a female Great Dane or Bull Mastiff with little or no adoption fee?

Ohio or surrounding area - We have adopted 2 dogs already, one from the pound and another we took in for a friend. Both are smaller breeds and we have a large home on a 2-lot property. We'd love to give a loving home to a female Dane or Mastiff. Prefer they be fixed if there is an adoption fee, but will cover the expense ourselves if there is no fee. Thanks!