You have a few options- off the shelf je's from aircooled.net or European Motorworks. Custom pistons are something that I do all the time. Aircooled.net also has super squish pistons too. As far as cast pistons, you have Keith Black as a cheap and light alternative to the forged JEs and Wisecos.
Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance