Admiralty lawyers deal with naval ordinance. 
Naval guns are ordnance.
HR Products has some weapons in various scales. Their line is cast white metal; the molds are old so the parts tend to be a bit rough.
The Scale Shipyard has some brass and cast resion items, mostly in 1:96 scale, and some are 1:48 scale.
The Floating Drydock and Loyalhanna Dockyard also stock weapons in various scales.