Welcome to the club Milkweed!
I know you asked for weed killer options...I can't help with that, but for ponds with too many cattails the common denominator is shallow waters. Ponds that fluctuate in normal pool levels can also contribute to the problem. A more permanent solution is to deepen the areas by the banks and out into the pond so that the cattails do not thrive.
I have read of folks having good luck with herbicides, but it is an ongoing effort. A backhoe can knock the problem down in short order.
Look into Arrowhead (AKA: Sagittaria latifolia, Wapato and Duck Potato) for a good alternative. It may not choke out the cattails, but would be nice once the cattails are removed. Make sure you get the native type, there are less adaptive imports that could waste your time and money.
Some arrowhead in juvenile form...
Here are couple pics of the mature Arrowhead. The small leafy stuff near the rocks is not part of the arrowhead plant..
Once established, it makes full stands or clusters. The above photos of the mature plant was taken after planting a single individual before it expanded. Here's the cluster after a full growing season...
It grows at the banks and down to about 18 inches of water.
