Have you seen about updating to a newer version of Mac OS X? I'm sure even Panther should be cheap now. Even 10.1 should be much cheaper, which would give you more app support.
Not much to choose from for 10.0.4, really. You could dig around for old versions of OmniWeb, but....I don't know where you'd find one.
I think iCab's probably your best bet. A new version was released just yesterday, in case you don't know. It's a big step up from the previous version (finally, real CSS support!)