there's a free demo, which should do the job. Just click the plus in the bottom left corner and select textedit (or the application you're making speak) and then hijack and record
Not exactly what you're looking for but it should do what you need it to do!
I found someone else online who found the answer. Here's a great way to create an automator application that will do it. NOTE: use one of the commenter's suggestions to avoid leaving AIFFs lying about.
I did this to a 9 hour novel and listened to it with Alex. Once getting used to the cadence, it was great.
Wow, so simple! This is the first time I've even opened Automator in 9 months since I switched to Mac, and I'm surprised how easy it was to use. Thanks, now I've got a way to spit out lyrics for this electro track I've been working on