Can you make up a good non-gender-specific pronoun in English?

From UsingEnglish.com
Language usage is something that people feel very strongly about, and we do get many emails about certain issues, so I am going to lay out the site’s language policies on some issues here so that users know where they stand.

Countless introductions to academic texts mention the issue of pronouns where the gender isn’t specified, and there are a number of ways of handling the issue:

1. Someone has left his umbrella.
2. Someone has left his or her umbrella.
3. Someone has left their umbrella.

The first is the traditional way, but it doesn’t allow for women. The second is all-inclusive, but it is wordy. The third is also all-inclusive, but it stands open to criticism that singular and plural are mis-matched.

I’ve seen a number of folks on fluther hassle people who use “their.” They act as if they don’t know people are not referring to plural persons, but to a non-gender-specific unknown person.

Anyway, whether you are a former English teacher or not, it’s a problem. Anyone have an elegant solution to this problem?