Re: replacing intake gasket & air leaks
About any old paper gasket material will work, and there is a pack at Ace Hardware with three sheets of three different material for cheap. I posted the part number here at one time, but you'll have to look for it. For the sealer you can use form-a-gasket, Seal-All, or silicone.
To make the bike more water resistant, seal off the mag cover, where the wires go into the mag, and the CDI where the wires go in and the plug lead goes out with silicone.