Drum Rack Mount(s) with Accessories

This rack mount is designed to fit any standard 1.5" tubular rack. You'll need a swivel nut and a tension rod for the mounts (hardware I used listed below). The swivel nut will need to be heat-pressed into the mount. The mounts and the accessories have a dovetail joint to secure one to the other. So far, I've created a headphone mount and a stick holder.
 

Mounts: there are two mounts. One for vertical posts, and one for horizontal arms/bars. I used Pearl swivel nuts left over from some marching drums I repurposed. I also had a bunch of Pearl 1-1/16" tension rods laying around that fit the swivel nuts. 
Headphone Mount: made with a little extra length to accommodate more headphone sizes, and holds Beyerdynamic DT-770 Pro headphones with no issues.
Stick Holder: made with enough room to hold 2 pair of 5A drum sticks (guaranteed). You can also fit a pair of 2B and a pair of 5B, but I'm unsure if 2 pair of these sizes will fit.
 

If I had to buy tension rods and swivel nuts, I would get ¾" (20mm) tension rods to 1-1/16" (28mm) tension rods. Any longer and it'll stick out too far after tightening. You'll also want to make sure you get swivel nuts that match the threading of the tension rods you get. If you need a 12-24 thread swivel nut, PDP makes a pack of swivel nuts that should work too.

I would suggest printing in (at least) PETG because it's flexible enough to spread the mounts to wrap around a rack post/arm without breaking, and it can withstand a little more heat that PLA if using this outside or in direct sunlight.