The Disk: Permanent Aeropress Filter by Coava
http://www.sweetmarias.com/sweetmarias/coava-disk-stainless-steel-filter-for-aeropress-brewer.html
The Aeropress doesn't really require any upgrades. The paper disc filters are inexpensive, work well, and a stack of them lasts a long, long time. But I was excited anyway to check out the Disk, a stainless steel filter for the Aeropress to use instead of the stock paper filters.
Recipes « World Aeropress Championship
http://worldaeropresschampionship.wordpress.com/recipes
"These are the top 3 Aeropress methods from the 2009 World Aeropress Championships…"