The portable unnoficial Dreamcast known as the Treamcast which has the built in LCD monitor and can be used in the car or anywhere has now been found on a Hong Kong site similiar in reputation to the great Lik Sang, the site is called Success HK the price is $173 or around ?94 which makes it the cheapest in the world for those interested.

They also have a review on their for it, heres a taster from that review:

The only thing that seems to be missing is the phone jack of the built-in modem, which is present in regular units. However, in the times of widespread DSL availability the most reasonable connection method is via the optional “Sega Broadband Adapter” a.k.a. the network card for the Dreamcast. Not all games support this though.

The TFT screen is small-ish, but perfectly alright for playing games. The speed of the TFT is ok, you shouldn’t have problems even with faster games. The only gripe I have is with extremely dark games like Half-Life, where the screen needs to be readjusted during the darker passages. Dark areas tend to become pitch black, while turning up the contrast has the side effect of turning everything else into blinding white. During scenes with normal room lighting in HL there’s no problem. Also, games that are generally more on the bright side are absolutely alright on this screen. In summary this screen is ok to play with, even though it has problems with very dark game situations. A more expensive TFT would’ve been better, but also more pricey.

More information and the review at Success HK