FYI - the normal cockpit covers Moss and others sells isn't waterproof, and hardly water-resistant. It's better than nothing, but once they get waterlogged they'll leak and at the very least leaves you with a soggy cover to deal with.
A "Weathershield" cockpit cover made by CoverCraft is completely waterproof - to the point that the water just slides off the material, even after a heavy storm (it's neat to watch, the water looks like mercury beading away). They're also light as can be and can be rolls up to fit in a zip-lock bag.
CoverCraft doesn't have a cockpit cover listed for the Elan but you might be able to find something else that fits. (FWIW I was buying from Cal Car Covers until I found out all they were doing was ordering from CoverCraft then printing their name on it - everything down to the stenciled model-number on the cover was identical to CoverCraft, just a little more expensive).