Geoff has a good point, Emily, in that some pro cameras have rather amazing resolution. While these cameras are expensive and may be mostly confined to fashion and architectural photography, it would be worth checking local photographers to find one that has a camera with a 50+ megapixel sensor, AND some experience in photographing artwork. Work such as yours should be photographed with lights that are polarized and with a lens that has a polarizer as well. Polarizing at both ends removes any trace of reflections or highlighting. You'd only need to transfer the image (via CD or USB stick) and size it appropriately.
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