Bubble pack (get a large roll form Staples - or similar)and clear waterproof packing tape. Make it double thickness and jam the end in the doors. A bubble pops now and then, but it's cheap, and lets the light in, acting like a frosted window. Much lower condensation than an expensive internal screen. the only downside is you may not want to use an external screen at a roadside stop, because you can't drive off in a hurry, without getting out.
We had a home made one for years and it was mauch better than the commercial internal silver one we have now
Ken Brown, September 2008
