Hi, Just got the law enforcer set - and wanting to get extra cars - but their doesn't seem to be many available - only 'add on's' for for instance I can not buy a batman car (as that comes in a set with Superman) only a flash one - or a wonder woman one. Same with limited edition wacky racers and disney tunes - I can only buy a Road Runner or Willw Coyote - but can not purchase a bugs or a daffy - is that right? Thanks, Justin.