get a magmount one from maplins, i have one and it's no more than 6 inches.... (setting myself up here) and it's great.
AVTEX - nothing else comes close ... http://www.acdctv.co.uk/product/aerials/avtex-12v24-volt-dc-boosted-sth3000-aerial/
i have a portable satelite dish and freeview box and 19" flat screen for my bus its never been fitted and so far its not even been in the bus yet. i may use it when my granddaughter gets a little older and comes away with us
