To my knowledge, images of ship manifests from Argentina are not online.
Centro de Estudios Migratorios Latinoamericanos (CEMLA) has a searchable database of the arrivals in Buenos Aires. The website is in Spanish. Here's a translated description of the records that are available:
The CEMLA database contains data of the arrivals to the port of Buenos Aires of passengers and immigrants who arrived in the period 1882-1932, 1938-1945, 1947, 1948, 1949 (partial) and 1950. There is little data from 1933-1937 because the books are now inaccessible.
* Data available are: surname, given name, nationality, marital status, age at arrival, profession, religion, port of departure, ship name, arrival date (and in some cases family members accompanying him on this trip.)
* Depending on the state of conservation of the lists. The state of destruction of some books has precluded recovery.
The birthplace started getting recorded in 1923. Except for some isolated records from 1910, we do not have information about the province or municipality of birth of immigrant arrivals until 1922.
CEMLA has apparently been digitizing records, so you may want to email them to ask if they're able to provide copies of the manifest pages or if there are plans to make them available online.