check these folks out ...
Cloyce Buchanan
Triad Magnetic Van Screens, Inc. magnetic screen for drivers &
4155 Friendship-Ledford Rd.      passenger door (listed in JC Whitney)
Winston-Salem, NC 27107          and screen for sliding door with zipper
(910) 769-2427                   down the middle. the sliding door
                                 screen is custom made for vw's. it has
Front Windows (fibreglas)        a magnetic tape on the borders and
 VS109 Vanagon ...... $34.95     velcro wraps around the sliding hinge.
 VB108 Bus .......... $34.95     i have the above for my westy and they
Side Windows (fibreglas)         work great! they also make mag screen
 VW203 Vanagon & Bus             for rear hatch. also non-vw screens.
   Sliding window ... $26.50/pr   <cwebb@teleplex.net (Charles Webb)>
 VC590 Vanagon Side door          Jon Hathaway <jonr@empire.net>
   w/Zipper ......... $51.86
Rear Hatches (fibreglas)         Shipping Costs: 1 item .... $4.29
 VW303 Bus .......... $47.03                     2 items ... $4.67
 VR302 Vanagon ...... $47.03                     3 items ... $4.90
They will also custom make items as well....

and for a temporary "fix", what i did was to get some fibreglas mosquito
screen door netting, and tuck it behind the rubber gasket on the inside
of the car. then masking tape the open side to the glass. worked for me.
:)