Devon4x4 sell Zu alloys (a Mach 5 type design) as well as MaxXtrac rims; however, these are alloys, if you want steel wheels then the choice is rather limited to either a modular design or the rather plain Land Rover ones. Most companies don't seem to cater for the 16" D2/P38 market.
What tyres were you thinking of fitting to the 18" alloys?