Can only get 4⁰ advance need advice.

Well, crud, yeah, most of those Google hits do eventually lead to "Discontinued". This link doesn't say so, though having seen all the others it's probably not good odds. :-( Guess the next step would be to watch Ebay, or make your own by bending, welding, and/or brazing. It's just a 12-point 7/16" box-end wrench with a stairstep shape to it; at least there are pictures all over the place.