Utility belt add-ons
It's easy to find or make pouches to attached to your utility belt for holding backup batteries, dog treats, and your essentials for the evening.
Missle dog backpack
Instead of Tank Girl's missle bra, I chose to put the graphically bold twin missles on my sidekick's backpack.
Use fabric or t-shirt scraps to make bandages. Take them outside and rub them in the dirt, or open your window and wipe the fabric on the sill. Mmm, authentic grime!
Other grimey places to to rub your costume include metal shops, mud puddles, salt flats, and car tires.