Check out this excellently crafted Doctor Who inspired TARDIS backpack created by Etsy user MadBoyWithBox. He is selling it for $166.96, and these are the specs he gives,
This is an entirely hand-made bag shaped like a 1960's British police box. It is made of a royal blue vinyl fabric and lined with a silvery-grey fabric. It's larger than my other bags to allow for more capacity, measuring 7 inches by 11 inches in size.
It has two clip-on backpack straps, with attachments on the side so that it can also be used as a handbag.