Ocean Aquarium of Penglai
Penglai initially housed four walruses; two females named "Maluda 玛露达" and "Malusha 玛露莎", along with two other unknown individuals (whose genders I do not know) seen only in news footage and a single image, who were sent to the aquarium at one year of age at around 2004 or 2005. Despite articles from 2007 seemingly stating that the aquarium only houses two walruses, females Maluda and Malusha, this facility evidently housed two bulls as of ≤ 2014, which could potentially have been either separate animals or part of the initial herd of four. I am not certain about whether or not any of these animals are still housed at the park or if they're still alive.
This facility held a bull and cow in 2019, and a solitary bull since then up until the time of this writing in 2022.