Looking for an ARCO EZ Rider gas tank. I'm assuming it takes the small squarish one that mounts between the rails but I don't know. Is this a metal or plastic tank? The bike model I have looks like the little white one in the top right (minus the tank) of the catalog pic's in the photo gallery (I cant figure out how to post it) If any one knows what is correct for this bike and has one or a substitute for original that will work please let me know.