Labradoodle Rescue & Goldendoodle Rescue
Hi Jen, I am sorry for your loss.
The very first step would be to submit an adoption application, even if there is not currently a dog listed in your area who might be a good match. There are always at least a dozen dogs in the program who are not yet listed, and new ones coming into the program every day.
In the meantime, make it a point to invite a friend or relative's dog over for a play date or better yet, a weekend visit. Your current dog may be missing her sibling, but that doesn't mean she would welcome any strange dog in her home. Many people are surprised when they bring in a new dog and find that their surviving dog isn't happy about it. Chances are that the one who is gone was there when the current dog came into the home, so the survivor grew up with the other dog and naturally misses that specific dog, not just having another dog to play with. Bringing in another dog usually works out just fine in the long run, but it's wise to do a test run first.