Try www.moseleymotorsport.com their prices look good and I'm getting a bonnet and bootlid from them if Geoff o here hasn't got any available. I got a pair of their DTM mirrors through today, very good.
I've seen a carbon fibre panel from the states but it was mental money. Not one in fibreglass though. I'd be interested in one as I'm just about to change the roof skin on mine to a non-sunroof one!!