Map holder for 800GS?

I would like to use a map holder on my 800GS. The "tank" is plastic so can't use a magnetic one. Don't want the expense of buying a tank cover (eg baglux) to clip a map holder to. The only ones I've seen attach to the top of a tank bag.

Any ideas?

http://www.touratech.com/shops/008/advanced_search_result.php?keywords=map+bag&x=0&y=0

http://www.touratech.com/shops/008/product_info.php?products_id=4979

The latter looks very much like a Touratech universal map bag I have myself.

The Barpack is very handy:
http://www.cycoactive.com/mc/bp3.html

This one
http://www.touratech.com/shops/008/product_info.php?products_id=5289

plus a velcro Map pocket
http://www.touratech.com/shops/008/product_info.php?cPath=15_98&products_id=5290
..on top should also do it.