Update: Following Diydave's suggestion, I got a 5/4 by 6"plastic board (free, by luck, 12' cut in half to make two blades) and attached it to my blade in the place of my steel blade. It needed different bolts because of the challenges of drilling square holes in the plastic board (see thread on that in Off Topic
) I used 2 inch long, 5/8 inch, grade 8 hex head bolts and big washers instead of the original plow bolts.
The plastic board worked great on its maiden voyage, I had to fracture the frozen slush piles into blocks with a shovel to where the blade could grab them, but it worked great to pull the piles down the alley way to the pasture. Where the corner of the blade would have dug into the concrete, the board just left grey marks. Depending on the winter and my plowing skills it might last a season before needing to be replaced. But for the cost of the bolts and a 15/16 socket it is a cheap alternative. No doubt the commercial blades are nice, but for what I hope is minimal use (thank you El Nino) this is fine. Thank you Dave!
BTW I ran out onto the lawn at one point with it, and it didn't dig into the established lawn. The fresh dirt and newly planted grass at the other end of the alley were another matter.