Epoxy. I use it often to create water tight bonds. It dries clear, costs about $2 a tube at nearly any store. Comes in two separate tubes, you squirt both out, mix em together and apply it. Let it set for at least an hour or two before use. Make sure not to put any epoxy on anything that will get hot (like a bowl). You don't want to be heating this up while smoking. So long as it isn't near the bowl it'll be ok.