Any clamp that holds a 3/8" rod will work.
I've made some suggestions below.
This is the most common mount I imagine most drummer/percussionists already have.
I've used this one the most, in many setups.
This is the best deal among all the mounts listed here.
Very similar in design to the LP model above.
Try positioning your Machine so the mounted beater is perpendicular to your stick. This gives you the most surface area to hit, and increases your accuracy.
The entire Machine can be hidden behind a music stand, or perhaps a cymbal... all you need to see is the red striking surface.
This mount is easy to attach to a cymbal stand and gives you the option of changing the angle.
Uses the Tama FastClamp Easy Set Up System.
The LP Claw is great to use when you want to mount your Miller Machine on a drum.
I've used it to put my Finger Cymbal Machine on the floor tom.
This Pearl mount is great when you want to mount two Machines close to each other.
The clamps are quick release so it's really easy to setup.
With The Miller Machine you can use most anything to play your triangle.
In the Broadway Production of The Addams Family, I had a solo triangle cue that I played while sitting in a chair, pretending to read a book.
I was 6’ away from the Machine and used a long piece of dowel to hit the mounted beater.
Here's a great option for mounting your Miller Machine directly onto a cymbal stand.
This adapter is small, easy to pack, and makes it super easy to place your Machine anywhere in your setup.
Similar to the Pearl mount above, the LP Mini Everything Rack is great for mounting two Machines close to each other.
This Tama Clamp gives you lots of adjustment options.
It's a bit more robust than you may need, but I like it when I want my Machine mounted in a very specific spot.
This Tama clamp is small and works great if you are in a tight space.
Just be careful because your Machine is closer to the cymbal stand and you'll need to make sure you have enough clearance.