All FM broadcasters are banned in the UK, the name of the broadcaster doesn't matter, be it iTrip or anything else. So no you can't get 'something similar'. But what can happen if you get one? You wont be thrown in prison, and I don't think the police will do iTrip-searches in peoples homes or cars, hehe.
You could instead try to get a cassette adapter, which makes it possible for you to connect your iPod to any stereo (in the car fx.) with a cassete player. It is not illegal, and they are available in many radio/tv stores.