I doubt whether this would be a viable solution, but you never know
http://www.emachineshop.com. Other avenues you may be able to try Nol; would be using a bandsaw or other mechanical saw fitted with a bimetallic blade suited to the cutting of copper alloys, or industrial engineering firms dealing with alloys use a number of tools to do it:
Okay 2 hours inthe basement last night to cut the first slab. Whew. And now I cant braze it. I also decided these caps are way to big and I'll get some smaller ones.
Diamond bladed angle grinder tbh, do the job fine, you'll just need some good eye protection and a good pair of gauntlets. Or alternatively, a cutting torch or as Frag says, an Arc (plasma) cutter.
I had a diamond blade on a sawzall trying to cut through .120 DOM tubing. took me an hour or so and i broke about 4 blades and totally wore about 3 of them.