There really are no cheap CNC milling machines that can cut copper at any good depth/speed.
I was looking into
this one, and it is in GB so it might be easier to ship it to you than something from the US or elsewhere.
Looks sturdy, relatively light (55kg) compared to other mills (you need lots of mass to control vibration anyways), powerful, available in metric, ect. I wish they had metric mills in the US, the stupid imperial system is too tough to use effeciently, especially since half my endmills are in mm
.