Clunks.....
I am not personally going to use a clunk. I need to have a fixed pickup so that I can roll the plane inverted to kill it.
However, we have been using film cannisters as fuel tanks here in the mid-south (fuji film cannisters). Inside them we have successfully used Cox Dragonfly clunks (hard to find), homemade clunks (kinda fiddly) and turned down fullsize clunks. When you turn a fullsize down (can use a lathe or a drill press) make sure to make it smaller in diameter, and to make the tip much pointier. This will make sure that the tip of the clunk will pick up the last little bit of fuel in the tank.
Good Luck.