I'm looking for a link to a specific story or parable.

It's about two people who love each other.  She has beautiful hair,
which she cuts off and sells to buy her love a gift.  Unknown to her,
he has bought her a mirror so she can see her hair better (or maybe he
bought her a brush to comb it?), and this gift is now useless for her.
 He likewise sacrifices something to buy the mirror (or whatever) that
makes her gift to him useless.

An acceptable answer will have a link to a concise and well-presented
version of this story (something I could email to a friend).  I'll pay
double for an answer within 2 hours of posting this question.

The story that you're remembering is "The Gift of the Magi," by the
great short story writer O. Henry (a pen name of William Sydney
Porter).

Online Literature: The Gift of the Magi
http://www.online-literature.com/o_henry/1014/

A free audio version of the story may be downloaded here (scroll to
the lower section of the page):

Librivox: The Gift of the Magi
http://librivox.org/the-gift-of-the-magi-by-o-henry/

My Google search strategy:

Google Web Search: "gift of the magi"
://www.google.com/search?hl=en&q=%22gift+of+the+magi%22

I hope this is exactly what you need! Please request clarification if
I may offer further assistance.

Best regards,
pinkfreud

Darn.  I was hoping the story would be shorter, like a fable or
parable.  I guess I must have seen a kids' version of it in a cartoon
or something and it must have stuck.  It's too long for me to use the
way I wanted to.  Also, I missed my deadline.

None of that's your problem, however.  I don't quite understand the
rating system, but any answer is a great answer.

Yes indeed, and in 19 minutes!

He pawned his pocket watch to have the money for ... (I think it was a
brush), and she had sold her hair to buy him a watch chain.

Should have been "any CORRECT answer is a great answer."

Thank you very much for the five stars and the nice tip!

~pinkfreud

I'm glad the story is long because that's such a great classic! :)