I have yet to meet an MR/VR headset that doesn’t hurt in some way, and halo style headbands have been critical to ensuring I’m able to work on XR development projects for more than 5 minutes at a time.
Valve’s Steam Frame is just as bad as the rest, despite being lighter weight and better balanced than both cheaper and more expensive options (Quest 3 and Apple Vision Pro being the platforms I’ve worked on most recently). Given my facial structure (I have a big nose, ok?) it’s plenty painful with the stock setup, and there are no halo straps available for purchase (official top straps are sold out, and they don’t resolve discomfort with clamping force through the facial interface).
So I made my own, inspired by the Annapro A2 for the AVP (which is a great balance between form and function, leveraging the existing Apple strap system on the first generation headset).
I scanned the headset with the Creality Raptor X, focusing primarily on the pivot mount and strap, in a gloriously janky dining room scanning setup. 
Meshed in Creality Scan and aligned in Blender with other scans; wearing the Steam Frame and wearing the AVP with Annapro A2, so I could compare exactly where things were sitting.
I started with a double sleeve design (with several printed iterations for dialling in the fit) just in case it might be necessary for maximum security (alternating the gap needed for installing the inner and outer sleeves to the outside and inside of the headband). After finishing the entire project, I don’t think it’s required. Would probably work just fine with a single layer, and it wouldn’t catch the elastic on the back edge while assembling. But I think the design works well enough as-is, and hopefully ensures installation security.
The scan of course has a fairly straight elastic (it was hanging vertically), but when worn, it arcs and curves quite a bit. I built out a simple Geo Nodes setup for bending the source models (I always work in stages for easiest non-destructive editing) to better match the natural angle of the Steam Frame headbands, and the results are questionable. Haha. It helps, but when worn, the elastic still bends further down when exiting the 3D printed mounting assembly, and installation is a pain (kinda terrifying to install on a brand new headset, not knowing if the pivot points could turn out to be a weak point of the product’s industrial design!).
The headband itself, much like the inner and outer sleeves, was modelled as a single sheet of polygons, extruded using the thickness modifier, and subdivided, with an additional manual step after initial model generation to clean up the mesh a little. I ended up leaning into the dualistic modelling process (mounting pieces versus the halo band part), and used two layers of geometry to create a subtle gap between the pieces. Once printed, the band and outer sleeve is entirely one piece, and the strength seems perfectly balanced with the flexibility (printed in PETG).
Printed in PETG on a Bambu Lab P1S, the strength and flexibility of the 2mm headband seems to be well balanced. Though once installed, it’s not secure enough to wear entirely without the facial interface (which is how I use both the Quest and AVP), but it significantly improves comfort!
I added hook and loop fasteners along with spare padding from my existing Annapro AVP band, along with a cable tie to ensure the headset is supported directly from the front of the halo strap, not just by the pivoting anchors of the elastic straps. It doesn’t seem necessary, and the facial interface provides just enough stability without having to clamp onto the face, that it all feels reasonably solid. I’m pretty happy with the improved comfort! For me, at least. I did model it entirely for my head. 
Which is why I’m sharing the Blender file, not a print file. Play around with it, adjust for your needs, and share alike.
SteamFrameHalo.blend (147.1 KB)
License: Creative Commons Non Commercial