As of May 2015, people who own Mitsubishi Endeavors can look for replacement owner's manuals on eBay. Owners can also access maintenance and warranty information on Mitsubishi's website, but Mitsubishi doesn't post full owner's manuals online. In addition, the website requires each user to register a free account.
Another option to consider is Books4Cars.com, which carries a wide range of owner's manuals and other model-specific information; it's worth noting, however, that rare manuals sometimes cost more than $100. Although some websites post digital versions of owner's manuals online, Mitsubishi doesn't offer digital owner's manuals, which makes it difficult for people to share copies with other owners.