MestUp7

I don't have any pictures, but I have successfully done this many times. It's hard to get just the right size, but I'm sure with some practice you'll get the hang of it.

What you will need:
Aluminum foil
Pen tube
Screwdriver
Superglue
Drill

Take a medium size sheet of aluminum foil and roll it up into a lose ball, and then take the handle of a screwdriver and shove it down into the ball, making the shape of a bowl. Press down on the loose parts of your foil to make it a hard object. Then get a small drill bit and a drill bit the size of a pen tube. Drill the bigger hole in the bottom and the smaller hole on top of the bowl, right on top of each other.

Now take a normal pen tube and glue the one end into the hole on the bottom, and you're all set!

I used mine with a bong similar to this that I got from a restaurant in Mexico:



Sorry if this has already been posted, but I wouldn't know what to search for to find out if it was.