This is a remix of the excellent design "Oculus Quest 2 Elite Strap_V2_NAVIDA DESIGN", here: https://www.thingiverse.com/thing:4630780. I tested several designs from Thingiverse, and this was my favorite thanks to its simplicity and its comfort. It's a big improvement in comfort from the stock strap!
The main change I made was to include an integrated holder for a 5000mAh power bank. I also modified the tabs to hold the strap more reliably than the original design.
The power bank this is designed for is the PowerAdd EnergyCell 5000, just $15 on Amazon. I didn't want to go too big with the battery, I think this size is a good balance between battery life and bulk/weight. I haven't timed to see how much battery life I can get, but the stock Quest 2 battery is 3640mAh so this should more than double it.
The power bank just snaps right into place. Use a 1-foot USB-A to type-C cable to connect the power bank to the headset.
I recommend applying a thin layer of foam padding for improved comfort.
One word of warning: the supports are a real pain to remove. If you have a dual extruder, I would definitely recommend using soluble supports here. I was able to use normal supports but you have to be careful so as to not break anything when removing them.
I'm including the Solidworks files in case anybody wants to do a remix.