I just got this amazing holder in a bundle with some other gear.
Attachment 111983
Its a linhof 9X12 holder which has:
Attachment 111984
A pressure plate (!)
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An automatic flip up darkslide light trap (which pops up when you pull back on the slide)
Attachment 111986
A film ejector lever (one for each side)

This is incredible, and i wish i had one for 4X5....