Hmm, Have you considered using something like the Nokia Internet Tablets n800/n810.
They aren't that expensive, between $200 to $400.
There is a app called E
vince Document Viewer available for it that appears to support CBR & CBZ files.
I haven't tried it personally yet as my N800 hasn't arrived yet, but will update when I get the chance.
Can someone who has one of these tablets comment on on its usability when viewing comics.
Edit:
my horrible spelling strikes again.