Is it permissible for women to wash a deceased elderly man when there are no men available to do so?

The fundamental principle is that men wash men and women wash women. It is not permissible for a woman to wash a man, nor for a man to wash a woman, even if they are mahram (unmarriageable kin). If no one is available to wash the deceased, then tayammum (dry ablution) should be performed. If a man dies among non-mahram women, or a woman dies among non-mahram men, then tayammum should be performed. It is permissible for a husband to wash his wife and vice versa, but it is not permissible for a son to wash his mother or a father to wash his daughter after death. As for a living person who is ill, it is permissible for each to wash the other, provided the awrah (private parts) are covered.