Have you tried Wrapsol products? I bought one for my Sony PRS 600 and I've had no problems regarding the touch screen - or anythign else - so far. They take custom orders, sou you can buy screen protection, or even full scratch-proof protection for virtually any device. They handle screen protectors for touch screen devices such as Ipod Touch, Iphone, and others. So far they provide protection for Sony ereaders, Irex, Kindle and Ipads.
http://www.wrapsol.com/