If you choose to make a tool I'm sure you could come up with a substitute or fab something - like a large fender washer with screw holes in the right position. I had an extra retainer so that was the quickest/easiest thing to use at the time.
I got my bearing off of ebay at the time but Mrmoparts sells them.
http://www.mrmoparts.net/steering-column-bearing-upper-bearing-all-models/