I modeled and 3D printed this replacement part it several times at the local library. I've made the final design available for printing at www.shapeways.com (See link below). Of course, you can also model your own design if you wish to spend the time.

Shapeways BCG800XL Impeller Shop

Here's a video with some background on the Shapeways part.

UPDATE - Shapeways is no longer in business. Please look in the "What you need" section above for other parts sources