You could possibly find a welder that welds fuel tanks. You can also use tank lining chemicals. Kreem does work but it does not seem to last. I have used red kote and seems to be working well. Next time I need to line a tank I am going to try POR-15, I have used POR brand on car frames and am impressed with that product so I will give the tank liner a try.
I believe you will have to find the same model tank