Armorpax offers the twin Vickers guns and mounts to use on SAS Jeeps and the single mount for Airborne Jeeps. They need to think about offering a full kit for conversions with gun shields and extended range fuel tank kits and radio gear for the ETO versions. That would rock.
I don't know of a lot of Jeep accessories being offered in the aftermarket. But again, Armorpax has some universal US and British vehicle items like antenna bases and tools that would be great improvements or add ons to your Jeep.