Rather than doing all that, why not use the method ccf used and replace the tube rivets with solid rivets?What TFF said - That hawker tool is a dead ringer for my stainless brakeline double flare spinning tool. Well, after you cross it with a forged structural C-clamp (actually, have to say "G-cramp" if it is to be properly Bitish, of course) & spin grind the cones for the desired contour.
Point being, for maybe $90 - $150 and some fun time at the lathe, milling machine, with perhaps some spinning on the surface grinder, you can have a dead ringer for the original tool, to form original looking functional connections.
Dunno what your scrounging options are, but sometimes shopping fleamarkets and junk shops are productive for the raw materials.
If the facility exists to make your own dies, it might even be possible to start with one of the low-buck soft metal tube tools from china.
If spending over $30, be sure the tool is eccentric/spinning type, and was designed to include stainless brake lines.