Oh, okay. Yes, then there are loads of example c&d letters at chillingeffects.org.
Several of these folks are doing different things. Putting 2 and 2 together.... The ATK people seem to be primarily using Google Adwords, and they identify their attorney on their home page. Since they outrank you on your registered TM for certain Google searches, they should be your primary target.
You might consider consulting with the attorney who filed your registration application. Then again, that's the same attorney who still has a .com domain name of a relevant .gov site, and used to use that to drive people to his business. Given the various regulations that apply to attorney advertising, I personally considered that to be outrageously unethical. He has since tanked the web page there.
In any event, if you can break them down into categories, then you can work up a letter for each category which:
1. Identifies your registration
2. Explains how they are infringing your rights.
3. Cites a few relevant cases and outcomes.
and
4. Demands that they stop.
Laws change, and facts are often different in various situations. That's why you aren't going to find a fill-in-the-blanks type form for this kind of thing.