[WSSix]

Now that you mention it, I remember that thread. I have no idea where to get something like that though. Maybe McMaster Carr? You might be able to make it using a small grommet that'll let a bolt bass through. You'd have to seal the bolt to the grommet though. Maybe use the sealant you'll use on the tank cover. Use washers on either side of the grommet and it should seal together when tightened down.