I'm looking at this at the moment
Cortech - Tail bags Cortech Competition Accessories .
In case I need more storage for longer trips the Cortech mentioned above would make a nice 30 liter addition to my 55 liter tail case. Price is within reason ($81) and there's the posibility to upgrade another 40 liter by adding the saddle bags
Cortech - Saddlebags Cortech Competition Accessories too ($144).
Just my 2 cents.