Weldon Shank

I have a job coming up where I have to cut a few largish holes in 10 mm steel. I have a Fein magnetic base drill yet no broche. A ring around the tool shops told me that no one carries Fein broche so I ran Fein directly. After a long wait and the explanation that I should ask their dealers because they are not a shop :? I was told that the sizes I need, 28 and 35 have to be ordered from Germany....Fantastic. So I got myself an adaptor from the Fein quickin drive to a different drive called Weldon shank. Now I said to myself, I am set, I can buy any broche from any supplier ... yea right. I ask for a broach with Weldon shank and get blank looks. A search shows Weldon shank broche with a square sort of drive. On Hares and Forbes website however the drive on the Broche they carry is everything but square, you have two faces with the other two round, two flat faces with two holes in the others and so on..... Can anyone please explain what is this mystery and where to buy this stupid cutters? Your reply is very much appreciated.