We have made a two week sample of ticketing data available as open data; the data is available as a .zip file and can be accessed through this post on our Digital Blog: https://blog.tfl.gov.uk/2015/12/09/is-customer-flow-data-useful-to-developers/
The data covers two weeks in October 2015; 11/10/2015 to 24/10/2015 inclusive. The bus journeys dataset should include what you need. Please note that this represents all recorded bus boardings per stop (so for example, also includes contactless boardings, not just Oyster as specified in your request). Further, the data represents number of recorded boardings by bus stop by route, as opposed to occupancy.
The metadata file will give you a description of all the fields, and includes a lookup for each bus stop code.
Please note that in order to ensure we are complying with data protection legislation and to prevent the potential identification of individuals, all rows where less than 5 people have boarded a bus from a stop at a specific time have been inputted as 5 boardings. This may have the effect of inflating the overall count of bus boardings at certain stops.
Please do let us know if you have any questions.