Durston mills really are the way to go. Their nearest competitor is
Cavallin, out of Italy, but I understand they are now out of
business. My advice would be to look for a geared mill, a combination
mill, with both grooved and flat rollers, AND a removeable side
roller, that you can change out easily. With the removable side
rollers, you’ll be able to buy (or have made by a machinist)
additional rollers to make your own custom wire shapes.
These inexpensive mills on the market that have interchangeable
rollers are very labor intensive to change out, and do not have the
inherent strength and precision of a Durston mill.
I’d suggest buying the widest mill you can get (C150), or the double
D2 model if you can afford it.
These mills, if taken care of, will last a lifetime, and Durston has
a repair headquarters here in the US, in Arizona, which also has
good a supply of parts.