I was in a JTF Mega Discount Store (Peterborough) a few weeks ago and I'm pretty sure they had replacement blades for Stanley bull nose planes. I can't remember what sizes they had but I will probably be near there on Monday or Tuesday. If you can wait until then, I'll pop in, have a look and post the details. Unless you have one near you of course.
I guess I could make one but the time it would take would be hellish prohibitive. Any leads on these blades would be appreciated but I think they would only be old stock languishing on a shelf somewhere. I bought two of them in exactly this way couple of years ago but have lost one and the other is now worn out! I know you can buy them for the sort of price mentioned above but I can buy a new plane for that - I don't love the plane that much lol !!!