I got a bit carried away and spent �35 on a 3M Ventureshield kit for the tank from
here (you can get it for fairing and mudguard too).
You get everything you need to cover the whole tank (loads more than it says on the website) - leading edges, sides (between the grey panels and the main tank), tank pad area and a piece for round the fuel filler.
Yet to fit it, but I helped my brother do his Harley with it. It's dead easy, almost invisible and is tough as old boots. The 3M stuff is very stretchy and mouldable and will cover decals without a problem.
Of course you could just use insulation or duct tape!