Mike:
Keep an eye on eBay - search for "lathe parts", "lathe delta", etc. and even on the model number of the lathe you are restoring. There are always people parting-out old lathes and other machinery, and in many cases sell these items individually instead of a "fixer-upper" lathe that they can't guarantee performance. Make sure the seller is reputable (good feedback score), and ask questions, particularly regarding whether there is any damage to the shaft hole, keyway, and set screw areas, and that the pulley is 'true' without bends or distortion. I'm guessing you'll find at least one or two auctions for what you need in a period of 3-4 weeks....
Good hunting.....
Rob Wallace