Hey Pisces,
This is so simple to make I just made one for my overflow last week. here is a pic to show you the finished product.

from the bottom you have a threaded piece that screws into your bulhead, then you have the straight pipe going to a "T" then the cap on top and your elbow on the side. the water is going to be draining through the elbow and the cap on top with a hole in it is to adjust the water level. you can twist the cap with the hole in it to make the water lower or higher.I would not glue anything just make sure it is a very tight fit. Very easy to make and it works very well. The overall height should be about an inch under the top of the overflow.
Good luck!
-Jordan