So I printed these parts, and they are actually very strong, even in PLA, and even printed in the flat orientation shown. Printing a set of 4 wheels took about 20 minutes on my printer.
Since the original wheels on my Glowforge have not failed, I am not keen to destroy them just to get the bearings out to test this temporary replacement. I have other bearings around, but at least two dimensions are critical: the inner bore of the bearing must be 6mm to match the post, and the width of the bearing must be about 6mm to avoid vertical slop. The outer diameter of the bearing used is 10mm, but this part could be modified slightly to accommodate a very slightly different diameter. I did some searching to find an identical replacement, but haven’t found one with all dimensions exact. (Possibly this one would work, if you stacked two of them in each wheel: https://www.amazon.com/10-Pack-MR106-ZZ-Ball-Bearing/dp/B00GGQ594E )
I did a quick knife-edge test. Using a very sharp kitchen knife, I put the blade into the groove, put some downward pressure, and rolled the wheel back and forth rapidly on a smooth counter. The wheel split within a second of this.
I then tested one with the other side of the blade, which is about 1mm thick, square edge. The part did not separate at all.
The wheels are very smooth. (Knowing that these are rotary contact surfaces, I had exported the original model with a relatively high angular resolution.) They roll like marbles.
If I had a way to mount these on my Glowforge, I would already be cutting with these to see how they hold up in real life. But since I have taken this as far as I can for now, I will offer this:
Anyone who needs a set of replacement wheels, and who is not able to print their own, send me a PM and I will print a set for you to try. Be warned that these are not tested, and may fail again in short order. I cannot speak to whether trying these might affect your warranty, but I know the company is trying to resolve this issue for us, and hopefully you will not need to use these for very long.
You will need to extract the bearings from your original (presumably damaged) wheels, and press-fit them into these parts. I haven’t been able to test this, but I expect the fit will be very tight, so you would need to press them carefully and evenly, and might need to run a 10mm drill through the opening to enlarge it slightly, or perhaps heat the part with a hair dryer/heat gun.
All I ask in return is that you share your results back here so I can make any necessary improvements to the design.