(This suggestion came in from Jen... Thanks for the good ideas.)
I'll be attending an event that attracts hundreds of people from across the region, and I thought it would be good to post one of Sassafras' fliers there, but wasn't sure if the event organizers would approve. Then I hit on an idea that wouldn't require anyone's permission. I use a wheelchair, and if I get a couple of binder clips, I can simply attach the flier to the back of my chair, where it'll be seen by numerous people. I wanted to share this idea with you, because a modified version of it may work for other people.
Obviously, the majority of Sassafras' supporters don't use wheelchairs, but fliers could be attached to laptop cases, large backpacks, or other objects that are more-or-less rigid and at least the size of a flier. Then, as the people carrying those objects ride the Metro, attend sporting events, or otherwise travel around the region, Sassafras' picture will be seen by people who don't happen to live or work in parts of town that have been covered in fliers.
If you do write on your blog about my idea for attaching "lost dog" fliers to wheelchairs, laptop cases, etc, one thing you might want to mention is that it's easiest to keep a flier in place when there's a piece of cardboard behind the flier, and both the flier and the cardboard are inside a ziploc bag. At least that's how things worked for me.