I've found two more that do fairly well. You have to cut and paste your text into their text box. I had to use the Ctrl-C and CTRL-V on the PPC keyboard.
Flite and
SmartRead Mobile
Neither is high quality and both have their bugs and limitations, but they both work on my WM5 PPC-6700.
Flite is free. Smart Read Mobile is a ridiculous $35.
Robb