About the only thing you can do is inlet a piece. I would not use epoxy however, because it will leave a glue line and not give if there are differences in expansion/contraction between the stock and the patch, and that could open up the glue line or cause cracking. I'd recommend using TiteBond II or III since it has some give in this situation. You're still going to have some problem with finishing without showing the line, however you can mix the titebond with a little fine sawdust to minimize that. I'd suggest you try this out on a scrap piece - inletted patch, glue, finish, etc. to get an idea of how it will look on the stock.