Charley;

I've made a few overflows, and have cut the teeth without a template. The way i do it is to set up the fence behind the bit to regulate the depth of each cut, then use double sided tape to tape a ruler on the fence. I then also use double sided tape to stick a square piece of acrylic on the table to work as a stop on the side of the work. I then cut a notch, move the stop 1/2", cut again, etc. Using a straight cut 1/4" bit, you get 1/4" cut, 1/4" "tooth" etc by moving the stop 1/2" each time. Because of the ruler attached to the fence, you don't even have to measure or mark anything on the work. (My fence does not move on slides the way the nice tables are set up)

The double sided tape works great for this. I never heard of a template for it, but you could simply use an existing overflow, if you have access to one, as a template. In that case, you'd attach the overflow to your acrylic with the double sided tape, and use a flushtrim bit to rout the notches. It would definitely be faster than cutting, moving the stop, cutting, etc.

HTH
Matt