Have you contacted Sears? If you had the door professionally installed, have you contacted the Installer?
Now, granted, I don't have an automatic garage door opener but what little searching I did on the WEB, there seems to be an awful lot of people selling Universal Garage Door Openers these days. I DON'T know if there's any downside to getting a Universal Remote. (Like, do you need to replace ALL your remotes now? Do you need 'additional electronics' besides the remote? And will it work with your Opener's wiring??? See what I'm saying?) So be sure to talk to a few people about this BEFORE you buy unless someone else on this Forum wants to offer some insight into Universal Remotes. (Stay tuned for a few days ...)
In any event, here are just a small number of sites that may have what you SPECIFICALLY need, or at worst, have Universal Remotes.