I don't have a pic of mine but I used a 1" to 1&1/2" bushing coming off my dain line conected to a 1&1/2" plumbers "Y". I have 1&1/2" pvc out of the top of the Y with a slip cap (hole drilled with airline) and another section of pvc coming out of the bottom extending to about 4" below the water line in my sump. Very easy and works great. Should only take a few minutes to build. One thing that I learned is the taller the pipe coming out of the top, the better. I guess this allows more air to travel up. HTH
Edit:
Found a pic (not mine) but you can somewhat see what mine looks like. The RD is on the left. Again, the higher the pipe out the top, the better (at least IME). Also, some folks use a "T" instead of a "Y". I tried both and the "Y" worked best for me. Also, note that the "Y's" only come in 1&1/2" and up from what I could find. This is actually a good thing as the bigger pipe quiets things down and reduces splashing going into the sump. If you can fit a 2", I would think that would be even better.