I got some beautiful hardwood pickup rings made for about $45. Outer dimensions are typical humbucker size, inner cutout dimensions are typical mini-humbucker size. One caveat is that the rings are not beveled to match a guitar's top, they're flat, could break if screwed down too tight on a curved surface.
Here's a link to the maker's eBay store: http://stores.ebay.com/Woodguarden-Wood-Pickguards?_trksid=p2047675.l2563