Well, you could transfer the gasket over from the filter you're taking out. This might be risky, since you could break it when you remove it, and then be without one. Or you could go to the closest auto parts store and try to find a cheap filter with a matching gasket. I dunno. Its always best to inspect filters/parts in general before you buy them. At least if you went back to the Toyota dealer you'd get a proper filter for no extra charge, and no risk.