2013 TE310 Big Tank any suggestions??

Looking for something like the safari size

To my knowledge nobody makes a large tank, other than one thru Just Gas Tanks that is less than a gallon more. I have a template for a tank that mounts along the right sub-frame tube that would add a little less than two gallons, and need to be fabricated from aluminum, but haven't gotten that far yet. It would be nice to have some extra range just for riding around my home as most loops are around 100 miles. Just barely make it with the stock tank but always get really low on fuel by the time I find a gas station. I would not plumb the tank, just use it for capacity and do a manual transfer into the main tank, for simplicity sake. When I get my shop set up I may take a stab at making something. I have not found anyone in the US who is up to making a custom tank. The guys who make rally tanks for the big Euro events could do it, but for big bucks I think.