Product review (5 stars): Genuine GE part, perfect fit
Exact match, arrived in OEM packaging from GE. Yes, it can be a bit tricky to install, but nonetheless the part is a perfect fit.

Depending on how yours broke and whether or not everything inside the freezer caved in, remove all drawers, icemaker tray, etc. that pop or slide out. There's no need to unscrew or detach anything. The metal drawer slider that snaps into this divider part will need to be popped out of the old one (a quick job with a flathead screwdriver). Then slide into your new divider, you'll hear it click. It's easier to do this step before you install the new divider.

Also, make sure you have the metal crossbar in place before screwing in this piece. It does block your reach, but it won't fit in after you've installed the divider. (I tried.)

If you're having trouble reaching in, most models actually have "bins" zip-tied to the structures of the door sliders. You can cut the zip ties and pull out the bins, which should give you enough room to work (though a second pair of hands would still be helpful). If it's still too far for you, you can check Youtube for videos on how to remove the door (screws on the main slider I think) but I managed to get everything back together without going that far.