As mentioned in the other solutions, you can save, then exit to dashboard, then reload and choose the other two.
Unfortunately, as I've just found out, you can't back up your pre-ending save by copying it from one storage device to another. So, it looks like my current Hero is done for, since I'm saving that game to help others get any endings they're missing. Just send me a PM, and I'll try to get a session together to get you whatever endings you need.
UPDATE: 2014-12-31 - Looks like my save file is corrupted (thanks, cheap USB drives!), so I can no longer help others with their missing achievements. Sorry, everyone.