Regarding etching, any electronics hobby store should be able to sell you printable etch-resist transfer sheets, and ferric chloride etchant. You can get pure copper sheet at metal fabrication suppliers, or ebay.

Then you can use a computer to put your 12 words into a printable and possibly artistic / obscure design; print this on the transfer sheet, iron the transfer sheet onto the copper sheet, and dunk the sheet and etchant into a dish for ten minutes.

Beautiful, high-resolution result, and the copper sheet will last practically forever, even in the ground. Archeologists dig up well-preserved copper artifacts all the time after thousands of years.