Ok, after getting a halfway decent print of this part on my DLP printer I was able to compare it more closely to my original wheel. I ended up making the groove just a bit deeper.
Here is the latest (version 3) .STL file of the wheel, in case anybody wants to try printing some of these. As others have warned, please do not run your Glowforge unattended if you install these parts. You assume any responsibility for your decision to use this replacement part, but please let me know how they work out for you.
ReplacementGantryWheel_v3.stl (396.0 KB)