Not sold at retail, but you can browse Peak Design
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Creators cited with this
Creators who use this also use
Apple Watch (as camera viewfinder)
also used by 1 of them
Benro Mobile Tripod
also used by 1 of them

Moko Foldable Cell Phone Stand
also used by 1 of them
Peak Design bag
also used by 1 of them
Rambler (Google voice dictation)
also used by 1 of them

Roku Express (Fast Wi-Fi)
also used by 1 of them