Thank you Christiaan,
Bought one at lunch. They are brand new units from front runner including all plumbing and pump. Well worth it.
I have asked Shaneen to post on this forum when they have other special deals for G accessories.
They still have 4 or five units and then there is also a 51l unit on special. Not sure what the difference is except capacity.
I see FR does no longer list aux tanks for the G on their website so this might be your last chance to get an Aux tank.
Found the 55l unit but not under vehicle specific. Just shop fuel tanks. R11787.00
I suspect it is because the pump is not suitable for Petrol.
In fact I have not managed to find a bidirectional pump suitable for petrol.
Problem is you need a pump that can deliver at least 14l/min to fill the tank from your main tank when at the filling station.
Pumping it back would be no issue since you could use a facet pump (much less throughput) while you drive and have all the time.