The air cleaner is going to be really close to the underside of the hood. I don't have room for a standard wing nut, plus I wanted something custom. I came up with this idea and it turned out really nice.

I started with a 1/2" stainless button head bolt. The center was drilled out and tapped 1/4x20. Then the outer threads were machine away. Finally, I ground a flat on the top side and polished it. I had to open up the hole in the air cleaner lid a little but it fits good. The top of the fastener is pretty much flush with the top of the lid.