Then have the lady meet you, give her your extra ticket!

Then you both can go your separate ways at the Gala. Since all the ladies out here should have an interest!

I mean you're just trying to be a good guy, correct? You'd never be trying to have a lady there with you infringing on her free time, you're just trying to give your extra ticket away for a good cause...

You have already purchased the two tickets, correct?  Thus the funds have gone to their designated good purpose.  So how would a provider taking an entire evening off to serve as your date for this ball help "support a good cause"?  

Why even take a provider?  Why not just ask a friend or a work colleague to accompany you?

You may have the best of intentions here, but this looks and smells like a ploy to get a free date with a lady ...

You should compensate for time, especially as you are sending an ISO-type post.

And indeed, it only takes one to say yes to make the question worth while...
However, if you aren't even offering to combine this non-pay event with P4P time either before or after, then I think you are pushing your luck...

Perhaps this question would be better for a Craig's list ISO.
Seems like you'd have a better chance finding someone taking that route