Do you have a white dress? Wilma wears a white dress, and maybe you'd be able to get an orange wig from somewhere? A fancy dress place?
Other than that, Betty wears a baby blue dress and has dark hair...
Have you tried ringing a few fancy dress places? Get your yellow pages out! Sometimes ebay do next day delivery (if you're willing to pay for it)
Good Luck Hun,
Hugs x x x