What do you call portable? What's portable for one person isn't necessarily for another. Do you want widescreen (16:9 aspect) or are you happy with 4:3?
How important is colour fidelity and resolution?
For really good portability, widescreen with reasonable resolution and reasonable colour, you could look at something like:http://www.epson.com/cgi-bin/Store/jsp/Product.do?sku=V11H362020&BV_UseBVCookie=yes
That's just in your specified price range, although street price may be less.
If you have specific requirements, though, I'm sure some more suggestions can be made.