Tried finding a comparable fan with similar specs (size, CFM rating, 2 vs. 3 wire?)

 

I have a Nidec TA450DC series, and I noticed when I looked at the page for them, they implied imminent if not already discontinued.  I'd look at their page (it was an easy Google IIRC), and find a close match locally.  Nice fan-- heavy metal case, low draw for the rated CFM.

 

Perhaps you can get some more life from the fan by peeling the label and oiling there.