I have a new safe in production that can be used when a custom model is not available. It is called the VersaSafe and is 10" wide, 15" long and 10.25" high. It can be bolted to the floor behind the front seat or way in the back. Door opening is big enough for letter size file folders. Price is $269, but you get 10% off using the coupon code "GMTC" at check out.
Safe should be ready in a couple of weeks.