I worked in a toolroom on all sorts of stuff mate and if you're only cutting thin gauge aluminium or steel then you need to look at wire erosion or even laser cutting, if you put thin gauge stuff on a cnc miller they'll have a bugger of a time holding it down and the finish will more than likely be rough as the sheet will be vibrating. I'd say wire erosion would be your best bet and it'll more than likely be cheaper than laser cutting. Couldnt tell you what costs would be like though, but as you arent working to a size that would need to be measured and made that accurately, unlike if you were making a press tool then the cutout could be done in one run.
Dont forget its not just time on the machine, it'll have to be programmed for your shape so that time will have to be taken into account too.
With work the way it is now I'd have thought they'd have taken any work on, just google for wire erosion services in your area. But heres one to get you started
http://www.wmccm.co.uk/WMCCM/WMCCM/C...=17&tabindex=4