It looks like the factory seal does double duty as both the hatch seal plus it looks like it's also the trim around the the interior pieces. I need to actually lift a piece off the body seam to confirm what's actually needed. but this look seems to suggest that an Amazon molding won't do the job.I did find a 12mm bulb with the wing in EPDM, but it doesn't have what I see as the angle needed to support the interior pieces. More research needed before there's a final conclusion.
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To find the actual bulb size, particularly for a resto/recovery when I don't have a sample, a glob of modelling clay (read: Play-Doh) covered with packing tape (keeps it from sticking to the hatch...) offers a pretty reliable way to find the compressed size of the space where the bulb sits.