At the start of the year I came across a single-use benchtop bioreactor at a conference that was neither rocked or stirred but shaken. Do you happen to know who manufacturers such a system?

Based on your description, I think it is safe to say you saw the orbital shaken bioreactor system from Kuhner. I too have seen these systems in operation at conferences and the novel way in which they agitate. The system you describe as being benchtop is likely their SB10 which has a working volume of 3L to 12L. I understand there is also an SB50 and SB200 which will take you all the way up to 200L working volume to ensure scalability. Here is a link to more information; 

Kuhner SB10