If you reconsider at some stage then this ebay seller from NZ makes or used to make what you wanted:http://www.ebay.com.au/sch/crewie/m.htm ... ksid=p3692
He's the guy I referred to last time you asked this question:viewtopic.php?f=75&t=50430
His covers used to cost $65 + $10 postage, & his ads used to read:
"A custom made high quality nylon cover that fits exactly over the open area of the MX5 when the roof is down. Available in different colours (Red/Black/Blue/Green/Silver)
Saves having to unclip the tonneau cover & raising the roof to prevent the sun from cooking the inside of your car. Also stops leaves, dirt, dust & uv damage.
Comes in a small storage bag the same colour as the cover (the silver bag in my boot net auction photos shows the size they pack too!) & fits easily into the boot storage nets I sell.
Ideal when visiting friends, cafes, or to stop unwanted eyes peeering into your car!
These are waterproof but not suited as a permanent cover!
Fits all Mx-5 cars from 1989 - 2005
Airmail postage to Australia AU$10.00"