I have this kind of fan in my truck, plus a couple of equally worn spares. I had one opened up to find out how they are made. There is a cap on the inner side of the pulley that is spot-welded to the main tube. Once that is off, the bearing shaft can be pressed out of the pulley and mount. I also ground off the fan blade rivets and removed the end cap under it.
After much searching, I found a replacement bearing, and cheap, no less. Plus it has some interesting possibilities... The bearing is an NSK 885586 "water pump bearing". Cost was $20. It is physically identical except that it has an extra-long shaft sticking out of both ends. The shaft is made with special steel so it can be trimmed to fit without carbide tools.
What's interesting, potentially, is that the extra shaft length on the fan end can be used as a center hub for a different fan blade. For instance, a polymer fan or a flex-blade fan, or (in my case) one with more than 3 blades. (My truck has a car engine). The shaft diameter is 5/8" which just happens to be the most common pilot diameter on modern replacement fan blades. I haven't gotten too far along with this but I'm hoping to have it finished this month. Just replacing the bearing on a stock fan would be really simple.