A few years ago I made a headphone switchbox. It was popular enough that I added it for sale on Zynsonix. It uses a standard Hammond chassis which is made in Canada. There have been people looking for a more compact version. Unfortunately Hammond doesn't make a super compact extruded chassis from this line, however a fellow over at HeadFi, ScornDefeat, was able to find a smaller chassis that fits everything (just barely). I believe it's the same chassis as the Objective 2 headphone amp. The size is 3.15" x 5.25" x 1.37" / 80 x 134 x 35mm (LWH) and it comes in anodized black, silver, or blue.
Rather than Electroswitch in the previous build, the similar 3 pole Lorin CK-1460 is used, and rather than the flashier Neutrik NMJ6HC-S with silver hexagon design, the plain black NMJ3HF-S is used. These are all about the same size so should be interchangeable.
The knob is a 1/4" Kilo machined aluminum knob. I prefer the selector on the right as it's a little more natural to use the right hand to switch outputs.
One oddity to note is the chassis that came from Amazon had tapered head silver screws and the chassis screw holes needed to be threaded (Hammond chassis comes pre-threaded).
If you'd like to build one of these yourself, it shouldn't take longer than 2-3 hours. I recommend solid core 24 AWG wiring for headphone signal wiring inside of a chassis.
If you'd like one of these built for you for your headphone switching needs, reach out to Zynsonix.