Reviving an old thread here . . .
And here's the link to the sunshade I'm using, a Covercraft UVS100 that I purchased a few months ago from Cardid . . .
http://www.carid.com/covercraft/uvs100-silver-heat-shield-mpn-uv11259sv.html
No, not the least expensive option and I know I'd be getting another level of cooling performance with the sort of homemade external shields I'm seeing here. But this one has been performing very well and it can be deployed in a matter of seconds. Locked up inside the car, it's also not all that easy to casually steal.