For a 1/2" weldless fitting, you will need to make a hole that is just a hair bigger than 3/4". Step bits for larger sizes than that are pretty expensive, so people tend to either go with a hole saw, or get the cheap 3/4" step bit and enlarge the hole with a dremel tool or a file.
Honestly, you can barely get the individual parts cheaper than
here. The sweat and frustration that I invariably incur in the plumbing aisle is worth more than the coupla' bucks you might save. Even if you go the DIY route, just looking at the site will give you a list of what you need.
One other tip. If you are using a thick aluminum stock pot you can just drill the 3/4" hole, then put two nuts on one side of the nipple (don't that sound kinda erotic) and force it through by twisting and cutting threads. This worked well for me. I then JB welded the nipple in place and am very pleased with it. Almost as good as a weld-on.