Tiny but effective!,
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This review is from: 1/4" Black Adjustable Hot Shoe Mount Adapter For Camera (Wireless Phone Accessory)
The smallest I know of that really works.
I currently have a 430g, 5" field monitor incl. batteries on it with my Canon 5DII, and it works well without adding much bulk or weight to the set up.
However, I have reservations about how long it will last before stripping the plastic thread as it needs to be tightened firmly to hold the above weight at any angle.
If cheaper I'd have bought another as spare.