After much thought I decided she most definitely needed a bat mobile. We found a cheap "Cozy Coupe" on craigslist and spent a whopping $10 on it. From there, with a little graffiti spray paint from my store (art store, Jerry's Artarama) grafix paper for the details, fabric and gemstones from JoAnn Fabrics we were set. This was an easy Saturday project that cost no more than $20 total. Of course the cost varies on how much you spend on the car. We got lucky and for everything else I had coupons! Stinker now insists on eating her lunch in her batmobile while watching TV.
Tips: I found it was best to sand down the cozy coupe after taking it apart and before painting. Helps the paint stick. I used graffiti spray paint (Montana or Alien works) though I've heard of Krylon Fusion working too. The stencils were made from airbrush graffix clear sticky acetate and used on the car. I just printed out the symbol and cut. An Xacto knife gets the most precise cuts. Lastly, hot glue guns are awesome. Invest in one for crafting!