Having a converted passenger van, I wanted to be able to use/mount some curtains for occasional use.  Saw a listing on The Samba offering window screens with magnets.  Aha! thinks me, and I Google for a source of magnets.  Found a bunch of places selling all kinds.  My plan is to sew some into the hems around all my curtains, and to surround some nylon screens with some "edging" capturing some magnets under that, as well, for removable screens.
  I got 4 dozen magnets, about 1/8" thick by about 3/8 wide and 5/8 long..The cost was about $25.  Right now, I have some old curtains from a former van, a dodge, with bungee cords sewn into the top hem.  I just hang these onto the round clothes hangers, then stick a couple of magnets onto the bottom corners to keep them against the window frames..for now.  When I get to it, I plan on sewing the curtains to the proper fit for the vanagon, with the magnets spaced into the hems every 3-4inches..
  I've found plenty of other uses for the magnets, too..I stick my metal sunglasses case onto the dash with some, use a few for sticking down a map in sight of the driver, or directions, or a memo booklet...I made a little  "coambing" (nautical term) from a nice piece of teak I had in my scrap wood pile..stuck some magnets on the bottom, then I stuck it  onto the dash..just in front of the padded section...Now I can toss small things up there and not have em slid off.  
  Very cool, useful things,  magnets......especially in my van, which is metal, not plastic...
  Don Hanson