The place where mine leaks is in a corner where the tank hangs down. I doubt if tape would stick to the outside where it's corroded. I wonder if I could use some fiberglass cloth in the inside corner and cover it with JB Weld? I've also seen a few gas tanks on ebay but they're not for the 1-42. I wonder if some of the other 1-40 series tanks will fit it. They look pretty much the same as mine. Of course they may have leaks too.
Check the style of your and make sure you get the same thing as there were two distinct types. Late model 1-40 and 1-50 saws had a sort of divider to cover the front of the fuel tank and a oil tank with a manual pump attached as an add on. Other than that any 1-4X, 1-5X tanks without the oil pump are the same part number. Even the 200/300/400/500 tank front should work but the style is different and lacks the little "foot" on the bar side.
Mark