FYI: Home Depot has the 3" cut off discs.
Just as a word of caution, not all of the cut off discs carried by the big box stores have a high enough RPM rating for some of the higher RPM cut off/die grinders. Be sure to observe the RPM rating of the wheels you buy are adequate for your die grinder, lest they become a flying projectile.
Additionally, the cheaper cut off discs typically put more particulate in the air, quicker. My personal experience has been that the more expensive name brand discs carried by my local welding supply
and rated for cutting stainless steel, will put less particulate in the air and make up any price difference with their longer abrasive life.
Now lets talk about breathing protection. The throw away dust masks are about only good for fogging up your safety glasses. I use one of the cheaper 3M respirators, the exhalation valves to the side keep the saftey glasses from fogging up, and the seal conforms to your face much better, less chance of breathing all that cut off wheel/steel particulate.
JK thanks for heads up