Oh LisaJo,
Your post just tugged at my heart. Pets can be like best friends and losing one is very hard. The things we did with our loved ones, the places we used to share with them, can become almost haunted with memories.
Perhaps at some point you will be ready to find a new 'walking buddy' to adopt. Walking the dogs at the shelter is not a bad suggestion if you would not find it too painful. The dogs and shelter workers are usually thrilled to have volunteers.
You might also try a change of route. Maybe on the days you have time, go to a walking park, trail, or even mall. In my community there are a few walking/running clubs as well, which adds a social component. Even if you were only able to find companionship on the weekends it might help.
Being very goal oriented, I always found it easier to exercise if I had a race to 'train' for. Most communities have charity or 'fun runs' often sponsored by local fitness stores, where for a small fee everyone can come walk/jog/run a set course. Setting a goal and making a plan on how to get there is very motivating for some.
runnersworld.com has a list of events searchable by location/date/length...
I am very sorry for your loss.
