Ok... I think your asking about a bowl for your bucket, or as some of us like to refer to them ... gravity bongs. Basically you affix whatever you can that will seal the top when its burning, but will easily come off when your ready to suck it all down. All the setups I've seen have used the orginal bottle top with a hole burned through the top, and some sort of bowl is fashioned and the top is screwed on for burning and unscrewed for inhaling. Tin foil is used alot, but thats not healthy at all. The best is to buy a slide piece for a real bong, as they are relatively inexpensive, and are perfectly safe.