An update, because I know you have all been breathless with anticipation:
I happened to have both shoe goo and black polish so I went with that combination. The first layer blends in visually (bearing in mind people's eyes are pretty far away from my shoes. but a vast aesthetic improvement over electrical tape.) but shrank a tad as it dried so there's still a concave area where the wear was. It's still holding up after a couple commutes so I'll put on another coat or two to fill it in.
Also found a seam that had given way that I stitched back up myself.
Re: the suggestions about replacing them, I've never had much luck with cheap or used shoes. I don't see many ladies walking shoes at thrift shops and they need to be walking shoes not sneakers because I don't like sneakers because they're too mushy and I need a really good fit in the upper because my feet are bony and I've never had good luck with men's shoes maybe because my feet are narrow. To top it off, I need them to be black for work. And maybe there's something weird about how my feet break shoes in because used shoes always feel way different to me than new shoes. It's like the creases are in all the wrong places.
I did take a look on ebay, though, given the suggestions. I had been thinking since this model was from many years ago there wouldn't be any available but there are several, often for around $30-$60 depending on condition, so now I've got an alert set for the correct size and color.
Thanks y'all!