For our first road-trip in the car I fashioned a plastic kitchen storage tub (with lid) into something that sat on and bolted to the spare-wheel cradle. It worked as storage for a small toolkit / screenwash bottle / etc. Except it cooked the stuff inside, even with ~5-6in clearance from the radiator.
...so if you're going to do it you need to (a) ensure the ex-rad airflow vents downwards underneath the car quickly (or get an NSX-R style bonnet and vent it upwards); and (b) cover the front-half in foil to reflect as much heat as possible.
But to answer your question, there was never anything official nor after-market...not that anyone on here has identified, anyway...
PS - unless you're both >6ft there's a surprising amount of storage space behind the seats.
"No man with a good car needs to be justified"
Blue '08 FD2 CTR - big, ITR-sized shoes to fill...
Yellow '96 NSX 3.0 - oh was it worth the wait!
Black '99 ITR - well, I had to have another one, the first was so much fun. Miss this one even more than #1...
Blue '03 S2000 - SOLD, flawed but fun
Blue '04 Focus TDCi Sport - SOLD, very good fun for a diesel!
Black '00 ITR - SOLD, still missed
Red '98 Civic VTi - SOLD, probably still bombproof