aHa! Caught! The missing link!!!
OK, here's how you mod it:
Let's start with a normal fan. In this case I have cut the corners out of a Gentle Typhoon. Notice how the clip holder pushes only partly through the flange of the fan:
Now you need The Tool: a 9/32-inch drill bit. You can also use a 7mm drill bit, but that could be a little tight, so you might use an 8mm drill bit. Here is the GT with The Tool:
You grip the drill bit in your hand and slowly drill what is called a countersink hole partway through the flange. I suggest you practice on the intake side of a fan to get the feel of how it is done. If you are too strong or don't know when to quit, you can fully enlarge a hole, and that is not what you want to do.
This is what you want to do:
Note the the enlarged hole -- the countersink -- only goes partway through the flange. The idea is to accommodate the clip holder peg's larger diameter without letting it pull all the way through.
When you are done you will get this:
You do this for all four corners, and you put the clip ends through these pegs. Now your fan will fit onto a Noctua fin stack with Noctua clips.