Here's an easy to make Dzus Button forming tool.

This one turned out on a lathe, but it can be made on a drill press as well. All that's needed is a little care in finding center and drilling the hole square with the aluminum body.

The body is made of 1" OD 6061 T6 aluminum.
(6061 T6 is what you usually get when you buy aluminum. 7075 T6 works ok as well, but stay away from alloys with a softer temper such as 5054 T4. Aside from not lasting long, it doesn't machine real well.)

Cut the aluminum body to length making sure it's square on both ends.

Drill the body with a 3/8" drill on center.

Countersink the body with the usual 82 degree countersink.
A 3/4" OD countersink works well, but a larger one can be used if you're careful.

The pictures show a Phillips head F.H. 3/8-16 machine screw, but what you really want is an F.H. Allen machine screw (F.H. = Flat Head). A standard/non-stainless one. Most times black in color.

The Phillips will work, but life is a lot easier with an allen.

Shown in the pic as well is a stainless washer and nut.
You're better off to use a standard nut as the stainless nut galls and drags on the regular alloy Allen head.

To form the Dzus countersink in body sheet metal drill a 3/8" hole where the Dzus goes.
Assemble to the tool with the anvil (aluminum body) on the inside with the flat washer between anvil and nut.
Draw together until the Allen head is firmly bottomed out.
That forms the Dzus sheet metal countersink.
Remove tool and install the desired style Dzus.

Incidentally, DeWalt has a neat little drill set that incorporates a small pilot drill into the drills.
These work great for drilling sheet metal.
No center punch needed in most cases.

Note the formed hole in the sheet metal.
This was done in a piece of 18 gage sheet metal and it pulled the Dzus countersink in with no problems.
Most body metal is 20 gage so pulling in the countersink is easy.

One of the advantages with this tool is that no striking with a hammer is necessary.
Another is that the tool can be operated in very tight places.

Best of all, the price is right.
There's less than $2.00 invested in the one shown and the price is more than likely right around a dollar.

In my view this simple little tool beats the $35. + commercial tools that are on the market today.