BTW this is a 2005 troy-blit pulley assembly is 618-0624

There should be a part # stamped into the pulley. MTD likes to do that, sell completes that is. Much of the time I can reuse the pulley using the another spindle assy w/o as some of these get real pricey. I may have more info if the number isn't stamped, but it should be. Check the bottom.

it might just be easier and time efficient to replace the entire assembly. I presume there are bearings in there somewhere? If one part is leaving then, how far behind are the rest of the pieces?
BTW is the wear on the Pulleys or the Spindle or the Bearings? Is the wear a shared thing?
If you don't agree and you still want only the pulleys, you might try Grainger Supply.
Only here to help 8-D
M