Finding New Fan Blade for Pasco D119 Motor

I'm hoping someone might have an idea on finding a replacement for a fan blade. We have a rooftop fan that failed, and unfortunately the make and model of that fan assembly have been covered up by a roof sealant. The internal motor is a Pasco model D119. The fan blade is shown in four pictures and a crude mechanical drawing here:
http://pages.uschw.com/usenet/pasco-motor /
but it has no marking on it.
Essentially the original motor failed and burned out, and it warped the fan blade while it was dying. The motor was replaced with another Pasco D119, which works. But the old fan blade is not staying in place. It may have been mechanically damaged or lost its balance. It looks like it could be wobbling, or alternately it is traveling up the shaft of the motor and eventually begins to bang against the bottom housing of the fan.
We went to every HVAC distributor in the area and they were not able to find an equivalent blade without having the make and model of the entire fan assembly. I know it is a long shot, but I figure with so much experience in this group someone might know which make and model is shown in those pictures and might have some idea on where to find a replacement blade?
In case you are wondering why we don't replace the entire fan assembly with a new matched set of motor, blade, and housing, it's because the roof has a special sealant that completely covers the roof and the fan housing. To call in the roofing vendor to reseal a new fan is likely to cost as much as the new fan itself.
As a last resort, if there is not a possibility to replace the blade, does it make any sense to machine a hole in the fan motor shaft to secure the fan blade placement screw and prevent the fan blade from moving up or down the fan motor shaft?
nish
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