Cullmann produced an ingenious multi-functional extensible monopod shoulder support that was mounted via a removable shoe that screwed into the threaded tripod mount on the underside of the camera body. The two shoulder arms comprised two petals each, which could be splayed out to form four supports to enable the device to be used as a mini 4 legged tripod (quadpod ?), if you needed hands free camera support and preferred not to lug around a full size tripod.
I used it for most of my 1980s and 90s aviation photography, and found it indispensible for achieving a really steady pan with my 300mm lens. It more or less removed camera shake when using this and other lenses for working with static subjects, where a tripod was impractical. I never went on photography forays without it.
I've failed to find one on e-bay, but the company still operates - it might be worth contacting them; see details below.
CULLMANN GERMANY GmbH, Catherine Brandt, Waldstr. 12, 90579 Langenzenn, Deutschland. Tel: +499102-99959-32
I hope this helps,