yeah, a bilge plug - it's almost to your description, but it's not quite a wingnut, but a single lever that locks the plug in place.  believe it or not, it was actually recommended by gowesty after i called them looking for a replacement cap.  this was their alternative after the caps became extinct.

On Friday, May 20, 2005, at 03:56PM, Tim Demarest <tim.demarest@pobox.com> wrote:

>
>A bilge plug? It that one of those rubber stoppers with a wing-nut to
>tighten it up?
>
>(If that's not a bilge plug, then you capless listees might want to try a
>"rubber stopper with a wing-nut to tighten it up" :-)
>
>At 03:32 PM 5/20/2005 -0700, Dusty Edwards wrote:
>>i, personally, have been using a bilge plug from a boat (that works great
>>btw...),
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