First of all let me point out that glow discs suck. What you want to do is buy LED Lights. They are tiny electronic light sticks that can turn on and off and last for approximately 20 hours. They can be seen quite clearly 400 feet away in the dark of night. To attach them use a small piece of duct tape. I suggest you tape them as close to the center of the top of your disc as possible. Some people tape them to the bottom, but they are more easily seen from the top. If you have a roller disc, tape it to the bottom since rollers usually land bottom up.
To find LED lights go to the fishing department of your local sports store. They are reusable and I usually only have to buy 1 set per winter of 4-5. Now, you might find that your disc is slightly less stable with the LED lights, but it's not that bad, and it's definately worth the ease of play that the LED light provides. Sometimes wal-marts have them, but dicks usually always has them. The RED ones are the ones you want, the other colors are not so good.
A side note for the Off Season Water Works Glow League is that it starts the week after normal Water Works league ends and plays through the season right up to the week before normal leagues again resume. Tee Off is at 6:00pm, give or take a few minutes earlier and later in the year as the amount of light fluctuates. It is also a random draw non divisional doubles event. Meaning that all open and beginners are grouped together. You could have Laron one week and then be stuck with a small arm like me the next. But, in my opinion, it's the best league around.