For those of you who have accidentally put your tool into the blades of the extruder fan... (Pause for laughter)... I made this retrofit fan blade design. I'm using it now and it works great.
All you have to do is carefully remove the blade fins from your existing fan. I did this with an X-acto knife very carfully.
What you should be left with is a cylinder shape onto which this part should fit onto by pressure.
Carefully press fit the new blades onto the fan assembly.
Yes, while I was printing this I didn't have a fan going, but it's a short print and aftwards you will be back to 100% functionality.
I printed in standard resolution on a Replicator 2 with Makerware.