Riccardo,
These are, as you said, a little OT -- the manufacturer was either Hoshi or Hozan, and I remember them first showing up in the mid to late 80s. I was working for Sam Braxton at the time, building most of the wheels for the bikes that went out of the shop; we were pretty excited about them, as blades were all the rage at that time. These were much less tedious than hand-filing the spoke holes, and much less destructive than the press that DT sent out. Built a set of short ones on XT hubs to run on my mountain bike -- they lasted almost a week. The hub flange didn't fail, but several spokes broke at the bend. I don't think they still exist; perhaps you could take a longer DT Blade, cut the head off and bend it into the "z" shape? Or just rebuild the whole wheel...
Regarding flange failures, I rode for three or four years on a pair of 28 spoke Wolber Profil A rims with DT blades and slotted OMAS ti hubs, radial front and non-drive side rear. Crits, road races and even training rides back when I could still get Corsa CXs at wholesale. I'm 6', was about 175 lb.. at the time, and never even had to true the wheels. Perhaps I was lucky...
Good luck --
Derek Vandeberg
Bigfork, Montana